TIRES

Abstract

Pneumatic tires, including: a sidewall rubber that is provided on each of the sidewall sections of the pneumatic tire and covers one carcass ply of the pneumatic tire from an outer surface of the tire; and a two-dimensional code provided on a surface of the side rubber, wherein the two-dimensional code has a configuration in which a dot pattern is formed by two types of grayscale elements that are distinguishable from each other by irregularities on the surface, and in which a dot hole is engraved using light corresponding to a dark element of the grayscale elements, the side rubber is a diene rubber comprising butadiene rubber, and If A is a mixed quantity of butadiene rubber and B is a mixed quantity of carbon, each relative to 100 parts by mass of the diene rubber contained in the side rubber, then a ratio A / B of the mixed quantity A to the mixed quantity B and a hole depth D (mm) from an opening of the point hole to a hole bottom of the point hole satisfy a relationship of 1.1 ≤ (A / B) / D ≤ 6.0, where a perforated wall surface of the hole is provided in such a way that the hole cross-section decreases from the opening to the bottom of the hole, and a hole wall angle at a cut section of the dot hole, obtained by cutting the dot hole through a plane encompassing a hole center axis in a depth direction of the dot hole, is 10 to 50 degrees with respect to the depth direction of the dot hole, wherein a thickness of the sidewall rubber on a first side in an area where the two-dimensional codes are provided is greater in a tire radial direction than that on a second side, the second side being a side opposite the first side, and the cut section is a cut section along the tire radial direction, and of the hole wall angles of the point hole on the cut section, a hole wall angle θ1 on the first side in the tire radial direction is smaller than a hole wall angle θ2 on the second side in the tire radial direction.

Description

Technical field

[0001] The present invention relates to a pneumatic tire and in particular to a pneumatic tire which includes a two-dimensional code engraved on a sidewall section of the tire. State of the art

[0002] In recent years, a proposal has been made to provide a two-dimensional code, in which information is recorded, on a sidewall section of a pneumatic tire (hereinafter also referred to simply as a tire). The two-dimensional code can include more information than a one-dimensional code. Thus, various information for managing the tire can be included in the two-dimensional code. A technique has been proposed for engraving a sidewall section with a predetermined pattern using dot holes to create a two-dimensional code consisting of a pattern of grayscale elements in the sidewall section (Patent Document 1).

[0003] The two-dimensional code, formed by engraving the sidewall section with a predetermined pattern of dots, is protected from disappearance unless the sidewall section wears down, thus enabling effective tire management. Patent document 2 describes a pneumatic tire with a two-dimensional code engraved on a sidewall section of the tire. Patent document 3 describes a rubber tire with a sidewall, the sidewall comprising a coded matrix symbol. Patent document 4 describes a laser-markable rubber article containing at least one rubber compound composed of at least one diene rubber and at least one laser-sensitive pigment. Bibliography of patent documents Patent document 1: WO 2005 / 000714 A1 Patent document 2: DE 11 2019 003 062 T5 Patent document 3: DE 20 2015 009 105 U1 Patent document 4: DE 10 2009 044 718 A1 Brief description of the invention: Technical problem

[0004] Although a pneumatic tire equipped with a large number of holes for a two-dimensional code may be readable when the tire is brand new, the readability of the two-dimensional code can decrease as the tire rolls and is subjected to a load in an outdoor environment. "Reading a two-dimensional code" refers to reading a two-dimensional code using a two-dimensional code reader, such as a mobile device. "More difficult to read" refers to frequent failures to read the two-dimensional code. The two-dimensional code provided on the pneumatic tire is used by reading the information recorded in the two-dimensional code while the pneumatic tire is in use.Therefore, if the tire is used for an extended period, cracks can form and propagate in the dots of the two-dimensional code, creating irregularities on its surface. This undesirably hinders the differentiation of the grayscale elements, making the two-dimensional code harder to read. Thus, it is preferable to prevent the two-dimensional code from becoming harder to read when the tire is used for a long time.

[0005] Furthermore, each of the puncture holes has a shape that is recessed into the surface of the sidewall section. This shape is not advantageous with regard to the durability of the sidewall rubber and consequently the durability of the pneumatic tire, since cracks develop in the puncture holes during tire use and propagate in the thickness direction of the sidewall rubber and further along the surface of the sidewall section.

[0006] In light of the foregoing, the objective of the present invention is to provide an air-filled tire in which a two-dimensional code is engraved and which can prevent the two-dimensional code from becoming harder to read, even if the air-filled tire is used for a long period of time. Solution to the problem

[0007] One aspect of the present invention is a pneumatic tire. The pneumatic tire includes: a sidewall rubber provided on each of the sidewall sections of the pneumatic tire, covering a carcass ply of the pneumatic tire from an outer surface of the tire; and a two-dimensional code provided on a surface of the sidewall rubber, wherein the two-dimensional code has a configuration in which a dot pattern is formed by two types of grayscale elements, distinguishable from each other by irregularities on the surface, and in which a dot hole is engraved using light, corresponding to a dark element of the grayscale elements.

[0008] The side rubber is a diene rubber including butadiene rubber, and if A is a mixed amount of the butadiene rubber, and B is a mixed amount of carbon, each relative to 100 parts by mass of the diene rubber contained in the side rubber, then a ratio A / B and a hole depth D (mm) from an opening of the point hole to a hole bottom satisfy a relationship of 1.1 ≤ (A / B) / D ≤ 6.0.

[0009] According to the invention, a hole wall surface of the point hole is provided such that a hole cross-section decreases from the opening to the hole bottom, and a hole wall angle at a cut section of the point hole, which is obtained by cutting the point hole through a plane that includes a hole center axis in a depth direction of the point hole, is from 10 to 50 degrees with respect to the depth direction of the point hole.

[0010] If S 70an area of ​​a hole cross-section of the point hole at a position separated by 70% of the hole depth D from the opening in the depth direction of the point hole, and if S0 is an area of ​​the hole cross-section at the opening, a ratio S 70 / S0 preferably from 0.2 to 0.5.

[0011] According to the invention, the thickness of the sidewall rubber on a first side in an area where the two-dimensional codes are provided is greater in a tire radial direction than that on a second side, wherein the second side is a side opposite the first side, and the cut section is a cut section along the tire radial direction, and of the hole wall angles of the point hole on the cut section, a hole wall angle θ1 on the first side in the tire radial direction is smaller than a hole wall angle θ2 on the second side in the tire radial direction.

[0012] Preferably, the cut section is a cut section along a tire circumferential direction, and of the hole wall angles of the point hole on the cut section, an absolute value of a difference between a hole wall angle θ3 on one side in the tire circumferential direction and a hole wall angle θ4 on another side is smaller than an absolute value of an angle difference between the hole wall angle θ1 and the hole wall angle θ2.

[0013] Preferably, the 300% tensile modulus of the side rubber is 5.0 to 10.0 MPa.

[0014] Preferably, the nitrogen-specific surface area of ​​the carbon is 30 to 90 (m²). 2 / G). Advantageous effects of the invention

[0015] According to the pneumatic tire described above, it is possible to prevent the readability of a two-dimensional code from decreasing when the pneumatic tire is used for a long period of time. Brief description of the drawings Fig. Figure 1 is a diagram illustrating an example of a configuration of an air tire of one embodiment. Fig. 2(a) and Fig. 2(b) are diagrams illustrating an example of a two-dimensional code according to one embodiment. Fig. 3(a) and Fig. 3(b) are diagrams illustrating the shapes of the puncture hole obtained by cutting the puncture hole through sections along a tire radial direction and a tire circumferential direction. Description of embodiments

[0016] The pneumatic tire according to one embodiment is described in detail below.

[0017] In this description, "tire width direction" is a direction parallel to the axis of rotation of the pneumatic tire. "Outside in tire width direction" is a side in the tire width direction away from a tire equator line CL (see Fig. 1), which represents the equatorial plane of the tire. "Inside in the tire width direction" is a side in the tire width direction closer to the tire equator line CL. "Tire circumference direction" is a direction of rotation where the axis of rotation of the pneumatic tire is the center of the rotation. "Tire radial direction" is a direction perpendicular to the axis of rotation of the pneumatic tire. "Outside in the tire radial direction" refers to a side away from the axis of rotation. Likewise, "Inside in the tire radial direction" refers to a side closer to the axis of rotation.

[0018] In this patent specification, a two-dimensional code refers to a matrix display-type code that contains information in two directions, as opposed to a one-dimensional code (barcode), which contains information only in the transverse direction. Examples of two-dimensional codes include a QR code (trade name), a DataMatrix (trade name), a MaxiCode, PDF-417 (trade name), a 16K code (trade name), a 49 code (trade name), an Aztec code (trade name), an SP code (trade name), a VeriCode (trade name), and a CP code (trade name). pneumatic tires

[0019] Fig. Figure 1 is a diagram illustrating an exemplary configuration of a pneumatic tire 10 (hereinafter referred to simply as “tire 10”) according to one embodiment. Fig. Figure 1 illustrates a profile cross-section of one side in the tire width direction with respect to the tire equator line CL.

[0020] The tire 10 comprises a tread section 10T including a tread pattern, a pair of bead sections 10B on the respective sides in the tire width direction, and a pair of sidewall sections 10S formed on the respective sides of the tread section 10T and connected to the pair of bead sections 10B and the tread section 10T. The tread section 10T comes into contact with a road surface. The sidewall sections 10S sandwich the tread section 10T from both sides in the tire width direction. The bead section 10B is a section connected to the sidewall section 10S and located on the inside of the sidewall section 10S in the tire radial direction.

[0021] Primarily, the tire 10 includes a carcass layer 12, a belt 14 and bead cores 16 as frame members and a tread rubber 18, sidewall rubbers 20, bead filler rubbers 22, rim pad rubbers 24 and an inner liner rubber 26, which are arranged around the frame members.

[0022] The carcass ply 12 is formed from a carcass ply link made of rubber-coated organic fibers, wound into a ring shape between a pair of annular bead cores 16. The carcass ply 12 is wound around the bead cores 16 and extends to an outer side in the tire radial direction. The belt 14 consists of two belt links 14a and 14b and is provided on the outside of the carcass ply 12 in the tire radial direction. The belt 14 includes a belt link of rubber-coated steel cords arranged at a predetermined angle of, for example, 20 to 30 degrees with respect to the tire circumferential direction. The width in the tire width direction of belt link 14a of the lower ply is greater than the width in the tire width direction of belt link 14b of the upper ply.The steel cords of the belt links 14a and 14b run at an inclination in opposite directions with respect to the tire's circumference. As such, the belt links 14a and 14b are intersecting layers that serve to suppress expansion of the carcass ply 12 due to the air pressure inside the tire.

[0023] The tread rubber 18 is arranged on the outside of the belt 14 in the tire radial direction. Both end sections of the tread rubber 18 are connected to the sidewall rubbers 20 to form the sidewall sections 10S. The rim pad rubbers 24 are provided at the ends of the sidewall rubbers 20 on the inside in the tire radial direction and come into contact with the rim on which the tire 10 is mounted. The bead filler rubbers 22 are provided on the outside of the bead cores 16 in the tire radial direction and are inserted between a section of the carcass ply 12 before the carcass ply 12 is wrapped around the bead cores 16 and a section of the carcass ply 12 after the carcass ply 12 is wrapped around the bead cores 16. The bead filler rubber 22 extends from the bead core 16 along the carcass layer 12 in the tire radial direction to the outside.The inner liner rubber 26 is provided on the inner surface of the tire 10, which faces a tire cavity area that is filled with air and surrounded by the tire 10 and the rim.

[0024] Furthermore, a three-layer belt cover 30, formed from rubber-coated organic fibers, is provided between the belt link 14b and the tread rubber 18. This cover is located on the outside of the belt 14 in the tire's radial direction. The belt cover 30 can be provided as needed and is not mandatory. The number of layers forming the belt cover 30 is not limited to three and can be one or two.

[0025] A two-dimensional code 40 is provided on the surface of the sidewall section 10S of the tire 10 as described above. Fig. 1 is the position of the two-dimensional code 40 indicated by a thick line. Side wall section 10S and two-dimensional code 40

[0026] Fig. 2(a) is a diagram illustrating an example of the two-dimensional code 40 provided on the surface of the sidewall section 10S of the tire 10 according to one embodiment. Fig. 2(b) is a diagram illustrating an example of surface irregularities of the two-dimensional code 40.

[0027] The two-dimensional code 40 is engraved on the surface of the side rubber 20 in each of the side wall sections 10S by irradiation with light, such as a laser beam. The two-dimensional code 40 is formed from a dot pattern of two types of grayscale elements, distinguishable from each other by surface irregularities. The two-dimensional code 40 is a pattern formed by focusing a laser beam on the surface of the side wall section 10S to concentrate light energy through local heating and sublimation of the side rubber 20, and by engraving fine dot holes 40a into the surface. As in Fig. As illustrated in Figure 2(b), the dot holes 40a, which form the dot pattern, have a shape such that the hole cross-section gradually decreases in the depth direction. In the Fig.In the illustrated example 2(b), the shape of the hole wall surface is straight when the point hole 40a is intersected by a plane passing through a hole center axis extending in the depth direction of the point hole 40a, but the shape of the hole wall surface can be a convex or concave curvature in the direction of the hole opening. The point hole 40a is a hole whose opening shape is circular, including a perfect circular shape, an elliptical shape, or a quadrilateral shape, and when the opening shape is a perfect circular shape, its diameter is from 0.1 to 1.0 mm and its hole depth D is from 0.3 to 1.0 mm.

[0028] In the two-dimensional Code 40, a dot hole (depression section) is engraved by light in a unit cell region of a dark area beneath unit cells that define the grayscale elements of the two-dimensional code. No dot holes (depression sections) are provided in a unit cell region of a light area beneath the unit cells. In particular, the two-dimensional Code 40 has a configuration in which dot holes (depression sections) are engraved such that a dot hole (depression section) forms a dark unit cell region beneath the grayscale elements corresponding to a plurality of rectangular unit cell regions of identical size, subdivided in a grid-like form. Fig. 2(a) the dark area of ​​the unit cell area is represented by a black colored area.

[0029] The two-dimensional Code 40, which is in Fig.Figure 2(a) illustrates a QR code (trade name) and includes a dot pattern area 42 in which a dot pattern including two types of grayscale elements is formed. A blank area 44 containing light elements is provided around the dot pattern area 42, with the blank area 44 being surrounded by light elements of the grayscale elements. Fig. 2(a) Border lines are illustrated to clarify the outer edges of the blank area 44. The width w of the blank area 44 is preferably, for example, four to five times the dimensional size of a unit cell area in the dot pattern area 42. For example, the blank area 44 is preferably 15 to 25% of the width of the dot pattern area 42.

[0030] Since the in Fig.2(a) where the illustrated two-dimensional code 40 is a QR code (trade name), the dot pattern area 42 includes: a data cell area 42a in which data cells of the QR code (trade name) are displayed; and position capture pattern areas 42b in which position capture patterns are displayed.

[0031] In the Fig.In the illustrated example 2(b), the dot hole 40a, which forms the dot pattern of the two-dimensional code 40, has a hole cross-section that gradually decreases along the depth direction, forming a sharp square shape at the hole base. However, the hole base need not be sharp square; it can be flat. If the hole depth D of the dot holes 40a is greater than a predetermined depth range, the distance from the hole base to the carcass layer 12 decreases (the thickness of the sidewall 20 at the hole base position decreases), the degree of absorption of tire 10 deformation by the sidewall 20 decreases, and cracks are likely to be generated at the hole base due to long-term tire use. Furthermore, it is not desirable for the cracks generated at the hole base to propagate and reach the carcass layer 12, as this leads to a reduction in the durability of the tire 10.Furthermore, due to the cracks created in the hole base, the surface of the sidewall rubber 20, in which the puncture holes 40a are formed, is likely to exhibit irregularities. This adversely affects the light elements of the grayscale elements of the two-dimensional code 40, thus reducing the readability of the two-dimensional code 40. Additionally, long-term use of the tire makes it easy for foreign matter, such as mud, to clog the puncture hole 40a, further reducing the readability of the two-dimensional code 40. If the hole depth D is greater than the previously specified depth range, the readability of the two-dimensional code 40 decreases significantly due to the long-term use of the tire 10.On the other hand, if the hole depth D of the dot holes 40a is smaller than the previously specified depth range, the dark elements of the grayscale element of the two-dimensional code 40 become thin, and the readability of the two-dimensional code 40 decreases when it is brand new before the tire 10 is used.

[0032] From this point onwards, the hole depth D of the puncture hole 40a is set to a predetermined depth range. However, although the hole depth D of the puncture hole 40a can be set to the predetermined depth range, if the puncture hole 40a is irradiated with a laser beam, without taking into account the characteristics of the sidewall 20, such as the degree of sublimation due to laser beam irradiation, the hole wall surface of the puncture hole 40a may not be stably formed in a predetermined shape, and the decrease in legibility due to long-term use of the tire 10 may not be sufficiently suppressed.

[0033] When forming the dot hole 40a, it is necessary to focus the laser beam at the position where the dot hole 40a is to be formed in order to increase the energy density and heat the tread rubber 20 locally and rapidly for sublimation. At this point, the hole depth D of the dot hole 40a depends on the ease of sublimation of the sidewall rubber 20, the energy density of the laser beam, and the laser beam exposure time. When the sidewall rubber 20 is sublimated using the laser beam, the laser beam energy density is adjusted, and the exposure time is determined according to the ease of sublimation by mixing the raw materials of the sidewall rubber 20. In this way, the hole wall surface of the dot hole 40a can be formed stably in a predetermined shape, and consequently, the decrease in readability due to long-term use of the tire 10 can be sufficiently suppressed.

[0034] A diene rubber containing butadiene rubber is used as the raw rubber material for side rubber 20. In this case, the butadiene rubber sublimates readily upon laser irradiation, but carbon (carbon black), which is included as a reinforcing element (filler), does not sublimate readily upon laser irradiation. Consequently, the degree of sublimation ease of side rubber 20 is determined by the ratio between the mixed amount of butadiene rubber and the mixed amount of carbon. The degree of sublimation ease decreases as the ratio of mixed carbon to mixed butadiene rubber increases, and conversely, the degree of sublimation ease increases as the ratio of mixed butadiene rubber to mixed carbon increases.

[0035] If, in the embodiment, the mixed amount of butadiene is A and B is the mixed amount of carbon, each relative to 100 parts by mass of the diene rubber contained in the side rubber 20, and if the hole depth from the opening of the point hole 40a of the two-dimensional code 40 to the hole bottom is D (mm), it is according to the invention if the ratio (A / B) and the hole depth D satisfy the relationship 1.1 ≤ (A / B) / D ≤ 6.0.

[0036] The ratio (A / B) indicates the ratio of the mixed amount of butadiene rubber to the mixed amount of carbon. Therefore, if the mixed amount of carbon is large and the ratio (A / B) is small, due to the low degree of sublimation of the side rubber 20, the hole depth D tends to decrease under identical laser beam irradiation conditions (identical energy density and identical irradiation time). Since the hole depth D is set to a predetermined depth range, the laser beam irradiation conditions (energy density and irradiation time) can be adjusted as described above to modify the hole depth D.However, if (A / B) / D exceeds the range described above, because the extent of the adjustment of the energy density of the laser beam and the irradiation time of the laser beam exceeds a permissible range, it is not possible to form the hole wall surfaces of the point holes 40a stably in a predetermined shape, and even if the hole wall surfaces of the point holes 40a can be formed stably, the decrease in readability due to the long-term use of the tire 10 cannot be sufficiently suppressed.

[0037] For example, if, regardless of a small ratio (A / B), the depth D is increased such that (A / B) / D deviates from the numerical range, a large amount of heat is applied to the side rubber 20 because the laser beam irradiation time increases or the energy density increases. This increases the degree of deterioration of the hole bottom or hole wall of the point hole 40a and the surface of the side rubber 20 around the hole wall, making it easier to induce crack generation and propagation. Conversely, if, regardless of a large ratio (A / B), the hole depth D is decreased such that (A / B) / D deviates from the numerical range, the laser beam irradiation time decreases or the energy density decreases.However, since in this case the side rubber 20 can easily form the point hole 40a, the hole depth D of the point hole 40a and the shape of the hole probably vary due to the influence of the variation depending on the position in the mixed quantity of butadiene rubber relative to the mixed quantity of carbon, which impairs the readability of the tire 10.

[0038] Therefore, according to the invention, the ratio (A / B) / D is adjusted such that it is not less than 1.1 and not greater than 6.0. The ratio (A / B) / D is preferably not less than 1.5 and not greater than 5.0. It should be noted that the mixed quantity A is, for example, in the range of 50 to 70 parts by mass, and the mixed quantity B is, for example, in the range of 30 to 55 parts by mass.

[0039] In this way, by adjusting the ratio (A / B) / D to not less than 1.1 and not more than 6.0, it is possible to suppress the degree of deterioration of the surface of the side rubber 20 of the hole wall, and it is possible to sufficiently suppress a decrease in readability due to the long-term use of the tire 10.

[0040] According to the invention, the hole wall surface of the point hole 40a is provided such that the hole cross-section decreases from the opening of the point hole 40a towards the hole bottom, and a hole wall angle θ of the point hole 40a (see Fig.2(b)) is from 10 to 50 degrees on a cut section obtained by cutting the point hole 40a through a plane that encloses the hole's central axis in the depth direction of the point hole 40a. The hole wall angle θ is the angle of inclination of the hole wall with respect to the normal direction perpendicular to the surface of the side rubber 20 in the opening of the point hole 40a on the surface of the side rubber 20. The groove wall angle θ is the angle of inclination of the straight line connecting the opening to the hole bottom on the cut section. The hole wall with the hole wall angle θ can be stably formed by adjusting the laser beam irradiation conditions while ensuring that the ratio (A / B) / D is not less than 1.1 and not more than 6.0.If the hole wall angle θ is less than 10 degrees, foreign matter, such as mud, is likely to clog the dot holes 40a, and the readability of the two-dimensional code 40 is likely to decrease due to the use of the tire 10. Conversely, if the hole wall angle θ is greater than 50 degrees, since light entering the dot hole 40a is likely to exit due to reflection, the difference between the dark and light elements of the grayscale element decreases, and the readability of the two-dimensional code 40 is likely to decrease. Thus, the readability of the two-dimensional code 40 is likely to decrease further during long-term use of the tire 10.

[0041] If the laser is irradiated under identical conditions and the amount of butadiene rubber mixed is relatively large and the ratio (A / B) is high, the degree of ease of sublimation of the side rubber 20 increases and the hole wall angle θ tends to decrease. Conversely, if the ratio (A / B) is small and the amount of carbon mixed is relatively large, the degree of ease of sublimation of the side rubber 20 decreases and the hole wall angle θ tends to increase.

[0042] If, according to one embodiment, the area of ​​the hole cross-section is located at a position separated from the opening of the point hole 40a by 70% of the hole depth D in the depth direction, S 70 is and if the area of ​​the hole cross-section at the opening is S0, then the ratio S 70 / S0 preferably from 0.2 to 0.5. If the ratio S 70If / S0 deviates from the area described above, mud and the like will likely clog the dot holes 40a, and the readability of the two-dimensional code 40 will likely decrease due to its use. Furthermore, the light entering dot hole 40a will likely exit due to reflection, and the difference in grayscale between the dark and light elements in the grayscale element will decrease, further reducing the readability of the two-dimensional code 40.

[0043] The numerical range of the ratio S 70 / S0 can be achieved by adjusting the irradiation conditions of the laser beam, while the ratio (A / B) / D is set such that it is not less than 1.1 and not greater than 6.0.

[0044] According to the invention, the thickness of the side rubber 20 on a first side in the area where the two-dimensional code 40 is provided is greater in the tire radial direction than the thickness of a second side, the second side being the side opposite the first side, and if the cut section obtained by cutting the point hole 40a through a plane which includes the hole center axis in the depth direction of the point hole 40a is the cut section along the tire radial direction of the hole wall angle θ at the cut section, a hole wall angle θ1 on the first side in the tire radial direction is smaller than a hole wall angle θ2 on the second side in the tire radial direction. Fig.Figure 3(a) is a diagram illustrating the shape of the point hole 40a obtained by cutting the point hole 40a through the cut section along the tire radial direction, with the first side on the inside in the tire radial direction and the second side on the outside in the tire radial direction.

[0045] As in Fig. As illustrated in Figure 3(a), the hole wall angle θ1 is smaller than the hole wall angle θ2. By providing the point hole 40a, which has this shape, the hole bottom position of the point hole 40a shifts towards the first side (the inside) in the tire radial direction. Since the thickness of the sidewall 20 on the first side (the inside) in the tire radial direction is greater than the thickness of the sidewall 20 on the second side (the outside), cracks do not easily form at the hole bottom position, and crack development can be suppressed.

[0046] If, according to one embodiment, the cut section obtained by cutting the point hole 40a through a plane enclosing the hole center axis in the depth direction of the point hole 40a is a cut section along the tire circumferential direction of the hole wall angles θ at the cut section, the absolute value of the difference (θ3-θ4) between a hole wall angle θ3 on one side in the tire circumferential direction (see Fig. 3(b)) and a hole wall angle θ4 on the other side (see Fig. 3(b)) smaller than the absolute value of the angle difference (θ1-θ2) between the hole wall angle θ1 and the hole wall angle θ2. Fig. 3(b) is a diagram illustrating the shape of the point hole 40a obtained by cutting the point hole 40a through the cut section along the tire circumferential direction. Since the thickness of the sidewall rubber 20 is essentially uniform in the circumferential direction of the tire, the absolute value of the difference (θ3-θ4) in the circumferential direction is preferably smaller than the absolute value of the angular difference (θ1-θ2).

[0047] According to one embodiment, the 300% tensile modulus of the sidewall rubber 20 is preferably 5.0 to 10.0 MPa. Since the ratio (A / B) / D of the sidewall rubber 20, which has the tensile modulus, can be adjusted to the numerical range described above, the hole depth D (mm) of the dot hole 40a can be adjusted when using this sidewall rubber 20 such that the two-dimensional code 40 can be read, the degree of deterioration of the surface of the sidewall rubber 20 of the dot hole wall 40a can be suppressed, and a decrease in readability due to long-term use of the tire 10 can be sufficiently suppressed. The 300% tensile modulus is measured at room temperature (for example, 20 °C) at a tensile speed of 500 mm / minute according to JIS K6251.

[0048] According to one embodiment, the nitrogen-specific surface area of ​​the carbon contained in the side rubber 20 is preferably 30 to 90 (m²). 2 / g). By using carbon with a nitrogen-specific surface area of ​​30 to 90 (m²) 2 / g), the degree of deterioration of the hole wall surface of the pinhole 40a can be further suppressed, and a decrease in readability due to long-term use of the tire 10 can be sufficiently suppressed. The nitrogen-specific surface area of ​​the carbon is measured according to JIS K 6217-2. The sidewall rubber 20 preferably contains N-(1,3-dimethylbutyl)-N'phenyl-p-phenylenediamine or poly-(2,2,4-trimethyl-1,2-dihydroquinoline) as an anti-aging agent. Example, comparative example

[0049] To confirm the effects of the embodiments described above, various tires 10 (tire size: 195 / 65R15 91H) with different shapes of perforations for the two-dimensional Code 40 (specifically a QR code (trade name)) is manufactured, and the readability of the two-dimensional Code 40 during long-term use of the tire 10 is tested. The tire configuration of each tire 10 is as shown in Fig. 1 illustrates.

[0050] The dot 40a of the two-dimensional code 40 is a circular hole with an inner diameter of 0.5 mm. The QR code (trade name) had a size of 15 mm x 15 mm.

[0051] To simulate the long-term use of tire 10, a drum test was performed on each tire 10 on an internal drum under predefined conditions simulating long-term use. The drum test is a low-pressure test based on FMVSS139 (rim size: 15x6J, XL: 160 kPa and load: 100% LI). For the predefined conditions, which specifically simulate long-term use, the vehicle was driven 10,000 km at a speed of 81 km / h, during which tire 10 was irradiated with ozone at an ozone concentration of 100 ppmh. After driving, the legibility of the two-dimensional code 40 was checked using a mobile device and various methods of applying illumination light.

[0052] For each example and comparison example, ten tires were prepared after driving, and the two-dimensional code 40 was read using various methods involving the application of illumination. A read rate was determined as the ratio of the number of correct reads to the total number of reads of the two-dimensional code 40. The read rate is expressed as an index value in the examples, with the read rate in the comparison example serving as a reference (the read rate in the comparison example was assigned an index value of 100). Higher index values ​​indicate a higher read rate. The index is used as an evaluation of the readability of the two-dimensional codes when the tire is used for an extended period.

[0053] Table 1 below shows the results of the readability of the two-dimensional code 40 in relation to the arrangement position of the two-dimensional code 40. The mixing of the raw materials of the side rubber 20 is changed and the irradiation time of the laser beam is adjusted such that the groove depth D is set to be in the range of 0.5 to 0.7 mm.

[0054] “Groove wall angle θ (degrees)” is the average of the hole wall angles at 8 points on the circumference around the point hole.

[0055] “Groove wall angles θ1 and θ2” are the in Fig.3(a) illustrates the angles, and in the area where the two-dimensional codes 40 are provided, the thickness of the sidewall rubber 20 on the inside is greater in the tire radial direction than that on the outside. In non-inventive examples 1 to 3, the hole wall angles θ1, θ2 are identical (θ1=θ2) and set to 30 degrees. In non-inventive examples 4 to 8, the hole wall angles are also identical (θ1=θ2). In non-inventive example 10, the hole wall angle θ1 on the inside is set larger in the tire radial direction than the hole wall angle θ2 on the outside in the tire radial direction. [Table 1] Comparative example 1 Comparative example 2 Example 1 Example 2 Example 3 (A / B) / D 0,9 6,5 1,1 3,0 6,0 Hole wall angle θ (degrees) 30 30 30 30 30 Perforated wall angle θ1,θ2 θ1=θ2 θ1=θ2 θ1=θ2 θ1=θ2 θ1=θ2 Readability after long-term use 100 101 106 108 104 [Table 2] Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 (A / B) / D 2,3 2,3 2,3 2,3 2,3 2,3 2,3 Hole wall angle θ (°) 5 10 30 50 55 20 to 40 20 to 40 Perforated wall angle θ1, θ2 θ1=θ2 θ1=θ2 θ1=θ2 θ1=θ2 θ1=θ2 θ1 < θ2 θ1 > θ2 Readability after long-term use 104 106 107 105 103 109 106

[0056] The comparison between comparative examples 1 and 2 and the non-inventive examples 1 to 3 shows that by adjusting the ratio (A / B) / D to not less than 1.1 and not more than 6.0, the readability of the two-dimensional code during long-term use of the tire is improved compared to comparative examples 1 and 2.

[0057] The comparison between the non-inventive examples 5 to 8 shows that by adjusting the hole wall angle to 10 to 50 degrees the readability of the two-dimensional codes is improved during long-term use of the tire.

[0058] Furthermore, it is understood that if the thickness of the sidewall rubber 20 on the inside in the tire radial direction is greater than that on the outside in the area where the two-dimensional codes 40 are provided, the readability of the two-dimensional codes during long-term use of the tire is improved by setting the hole wall angle θ1 on the inside in the tire radial direction smaller than the hole wall angle θ2 on the outside in the tire radial direction according to the invention (see Example 9). List of reference symbols 10 pneumatic tires 10T tread section 10S side wall section 10B Bead section 12 carcass layers 14 belts 14a, 14b belt link 16 bead core 18 tread rubber 20 side rubber 22 Bead filler rubber 24 Wheel rim pad rubber 26 inner liner rubber 30 belt cover 40 Two-dimensional code 40a Point Hole 42 dot pattern area 42a Data cell area 42b Position detection pattern area 44 empty space

Claims

Pneumatic tire comprising: a sidewall rubber provided on each of the sidewall sections of the pneumatic tire and covering a carcass ply of the pneumatic tire from an outer surface of the tire; and a two-dimensional code provided on a surface of the sidewall rubber, wherein the two-dimensional code has a configuration in which a dot pattern is formed by two types of grayscale elements distinguishable from each other by irregularities on the surface, and in which a dot hole is engraved using light corresponding to a dark element of the grayscale elements, wherein the sidewall rubber is a diene rubber comprising butadiene rubber, and where A is a mixed quantity of the butadiene rubber and B is a mixed quantity of carbon, each relative to 100 parts by mass of the diene rubber contained in the sidewall rubber,A ratio A / B of the mixed quantity A to the mixed quantity B and a hole depth D (mm) from an opening of the point hole to a hole bottom of the point hole satisfy a relationship of 1.1 ≤ (A / B) / D ≤ 6.0, wherein a hole wall surface of the point hole is provided such that a hole cross-section decreases from the opening to the hole bottom, and a hole wall angle at a cut section of the point hole, obtained by cutting the point hole through a plane encompassing a hole center axis in a depth direction of the point hole, is 10 to 50 degrees with respect to the depth direction of the point hole, wherein a thickness of the side rubber on a first side in an area where the two-dimensional codes are provided is greater in a tire radial direction than that on a second side, the second side being a side opposite the first side, and the cut section being a cut section along the tire radial direction.and of the hole wall angles of the point hole on the cut section, a hole wall angle θ1 on the first side in the tire radial direction is smaller than a hole wall angle θ2 on the second side in the tire radial direction. Pneumatic tire according to claim 1, wherein if S70 is an area of ​​a hole cross-section of the point hole at a position separated by 70% of the hole depth D from the opening in the depth direction of the point hole, and if S0 is an area of ​​the hole cross-section at the opening, a ratio S70 / S0 is preferably of 0.2 to 0.

5. Pneumatic tire according to claim 1 or 2, wherein the cut section is a cut section along a tire circumferential direction and an absolute value of a difference between a hole wall angle θ3 on one side in the tire circumferential direction and a hole wall angle θ4 on another side is smaller than an absolute value of an angular difference between the hole wall angle θ1 and the hole wall angle θ2. Pneumatic tires according to one of claims 1 to 3, wherein a 300% tensile modulus of the sidewall rubber is 5.0 to 10.0 MPa. Pneumatic tires according to one of claims 1 to 4, wherein the nitrogen-specific surface area of ​​the carbon is 30 to 90 (m2 / g).

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