Tire

Abstract

To provide a tire improved in integrated performance of initial grip performance and peak grip performance on a dry road surface.SOLUTION: A tire comprises a tread part. The tread part has: two or more circumferential grooves continuously extending in a tire circumferential direction; a pair of shoulder land parts partitioned from each other by the circumferential grooves and a grounding end; a center land part positioned between the pair of shoulder land parts; and a width-directional groove, where a land ratio R in a grounding surface of the tread part is 0.50 or more and 0.80 or less. The tread part has at least one rubber layer made of a rubber composition containing rubber constituents, where the average value tanδA of loss tangent tanδ from -15°C to 20°C of the rubber composition measured under conditions of a frequency of 10 Hz, an initial strain of 0.1% and a dynamic strain amplitude of ±0.25% is from 0.40 to 0.60.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] For pneumatic tires, it is required to have high grip performance from the initial stage of running and to exhibit excellent grip performance (peak grip performance) when the tire warms up. Patent Document 1 discloses a rubber composition for a tire tread that contains a specific carbon black and is excellent in grip performance from the initial stage of running and peak grip performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a tire with improved overall performance of initial grip performance and peak grip performance on a dry road surface.

Means for Solving the Problems

[0005] As a result of intensive studies, it has been found that the above problems are solved by setting the land ratio on the ground contact surface of the tread portion and the average value of the loss tangent tanδ in a specific temperature range within a predetermined range.

[0006] That is, the present disclosure is a tire including a tread portion, the tread portion having two or more circumferential grooves continuously extending in the tire circumferential direction, a pair of shoulder land portions partitioned by the circumferential grooves and the ground contact ends, a center land portion located between the pair of shoulder land portions, and width direction grooves, and the land ratio R on the ground contact surface of the tread portion being 0.50 to 0.8 at 0Yes, the tread portion has at least one rubber layer made of a rubber composition containing a rubber component, and the average value tanδA of the loss tangent tanδ of the rubber composition measured under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25% is 0.40 to 0.60 at -15°C to 20°C. The present invention relates to a tire.

Advantages of the Invention

[0007] According to the present disclosure, a tire is provided in which the overall performance of the initial grip performance and the peak grip performance on a dry road surface is improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] A tire according to an embodiment of the present disclosure is a tire provided with a tread portion, the tread portion having two or more circumferential grooves continuously extending in the tire circumferential direction, a pair of shoulder land portions partitioned by the circumferential grooves and the grounding ends, a center land portion located between the pair of shoulder land portions, and width direction grooves, and the land ratio R on the contact surface of the tread portion being 0.50 to 0.8 at 0 Yes, the tread portion has at least one rubber layer made of a rubber composition containing a rubber component, and the average value tanδA of the loss tangent tanδ of the rubber composition measured under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25% is 0.40 to 0.60 at -15°C to 20°C.

[0010] By satisfying the land ratio on the grounding surface of the tread portion and the average value of the loss tangent tanδ in a specific temperature range, the obtained tire has improved overall performance of the initial grip performance and the peak grip performance on a dry road surface. Although not intending to be restricted by theory, the reason is considered as follows.

[0011] To improve the grip performance during cornering, it is considered necessary to increase the contact area of the tread and enhance the heat generation property of the tread portion. However, if the land ratio of the tread portion is too large, the rubber of the tread portion cannot be sufficiently deformed, and heat generation is less likely to occur, so there is a concern that the grip performance may rather decrease. Especially in the initial stage of running, since the tread portion is cold, it is in a state where deformation is even less likely to occur. The tire of the present disclosure has the following characteristics: (1) By setting the land ratio to 80% or less, it is possible to make the tread portion more likely to deform than the edge portion of the groove; (2) By setting tanδA in a temperature range corresponding to the tire temperature within a predetermined range, it is possible to ensure the heat generation property of the tread surface from the initial stage of running. And it is considered that, by the cooperation of these, a remarkable effect that the overall performance of the initial grip performance and the peak grip performance is improved is achieved.

[0012] It is preferable that tanδA and the land ratio R satisfy the following formula (1). Formula (1) 0.21 ≦ tanδA × R ≦ 0.45

[0013] By setting the product of tanδA and the land ratio R within the above range, the tread rubber can secure good rigidity and contact area, and the heat generation property is also improved, so it is considered that the grip performance can be further improved.

[0014] The rubber component preferably contains at least one of isoprene rubber and butadiene rubber.

[0015] By using a rubber component with excellent low-temperature properties such as isoprene rubber or butadiene rubber, it is considered that the rubber composition can be easily deformed even at low temperatures, and good initial grip performance can be easily obtained.

[0016] For the tire of the present disclosure, it is preferable that the length in the tire width direction of at least one of the land portions gradually increases from the outer side to the inner side in the tire radial direction. Further, the groove width on the tread surface of the circumferential groove located on the outermost side when the vehicle is mounted is L0, and the groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove located on the outermost side when the vehicle is mounted is L 95 When it is set as 95 it is preferable that L

[0017] By providing the groove width of the circumferential groove so as to gradually decrease from the outer side to the inner side of the tire in the tire radial direction, the tread land portion is easily deformed, and it becomes possible to easily generate heat generation in the entire land portion. Further, since the area of the bottom surface of the land portion becomes large, the reaction force can also be increased when the steering angle is applied. From this, it is considered that a large reaction force can be generated with respect to the grip generated on the tread surface, and the initial grip performance and the peak grip performance can be improved.

[0018] tanδA and L 95 / L0 preferably satisfies the following formula (2). Formula (2) tanδA / (L 95 / L0)≧1.20

[0019] L 95 By setting the ratio of tanδA to L

[0020] It is preferable that the rubber composition contains 5 to 50 parts by mass of a resin component and / or an ester plasticizer with respect to 100 parts by mass of the rubber component.

[0021] By blending a resin component and / or an ester plasticizer into the rubber composition, it is considered possible to improve the initial grip performance and peak grip performance in a well-balanced manner.

[0022] The rubber composition preferably contains 5 to 150 parts by mass of carbon black having an average primary particle diameter of 25 nm or less with respect to 100 parts by mass of the rubber component.

[0023] By blending such small-particle carbon black into the rubber composition, it is considered that the heat generation property is improved and the peak grip performance is further improved.

[0024] The rubber composition preferably contains 1 to 10 parts by mass of an organic crosslinking agent with respect to 100 parts by mass of the rubber component.

[0025] When an organic crosslinking agent is blended, the distance between crosslinking points becomes longer compared to crosslinking with sulfur, and it becomes possible to generate more energy loss, and it is considered that good peak grip performance can be obtained.

[0026] The tan δ of the rubber composition at 30°C is preferably 0.35 or more.

[0027] By setting the tan δ of the rubber composition at 30°C within the above range, it is considered that the grip performance can be further improved.

[0028] The complex elastic modulus of the rubber composition at 30°C is preferably 50 MPa or less.

[0029] By setting the complex elastic modulus of the rubber composition at 30°C within the above range, the heat generation property of the rubber becomes high, and the heat generation property of the tread surface can be ensured from the initial stage of running, so it is considered that the initial grip performance can be improved.

[0030] The glass transition temperature of the rubber composition is preferably -25°C or higher.

[0031] By setting the glass transition temperature of the rubber composition within the above range, it is considered that the energy loss corresponding to the frequency of vibrations generated during rolling under normal driving conditions can be increased.

[0032] In the tire of the present disclosure, the ratio of the total area of the circumferential grooves to the contact area of the tread portion is preferably 0.12 to 0.28, and the ratio of the total area of the widthwise grooves to the contact area of the tread portion is preferably 0.08 to 0.20.

[0033] By setting the area ratio of the circumferential grooves and the widthwise grooves within the above range, it is considered that the grip performance during cornering can be improved due to the deformation of the edge portion of the tread surface.

[0034] In the tire of the present disclosure, the ratio of the total area of the center land portions to the contact area of the tread portion is preferably 0.30 to 0.65.

[0035] By setting the area ratio of the center land portions within the above range, the rigidity of the tread surface can be ensured, so that the rubber can maintain an appropriate hardness against heat generation due to the edge component, and it is considered that deceleration during braking becomes easier.

[0036] In the tire of the present disclosure, it is preferable that the area ratio of the widthwise grooves and the sipes in the shoulder land portions is larger than the area ratio of the widthwise grooves and the sipes in the center land portions.

[0037] By making the groove area ratio in the shoulder land portions larger than the groove area ratio in the center land portions, the shoulder land portions are more likely to deform during cornering, and it is considered that the peak grip performance is further improved.

[0038] <Definition> A "standard rim" is the rim defined for each tire in a standard system that includes the standards on which the tire is based. In the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; and in the case of ETRTO, it is the "Measuring Rim".

[0039] The "standard inflation pressure" is the air pressure defined for each tire in a standard system that includes the standards on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0040] The "standard state" means that the tire is mounted on the standard rim and filled with the standard inflation pressure, and moreover, it is in a no-load state. In this specification, unless otherwise specified, the dimensions of each part of the tire are measured in the above standard state.

[0041] The "standard load" is the load defined for each tire in a standard system that includes the standards on which the tire is based. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY".

[0042] The "tread contact end" is the outermost contact position in the tire width direction when a standard load is applied to a tire in the standard state and it contacts the plane at a camber angle of 0 degrees.

[0043] The "land area" in the tread part refers to the area partitioned by the tread contact end and a plurality of circumferential grooves continuously extending in the tire circumferential direction. For example, when there are two circumferential grooves, the land area is divided into a pair of shoulder land areas and the center land area sandwiched between them. When there are three circumferential grooves, the center land area is further divided into the land area on the inner side of the vehicle and the land area on the outer side of the vehicle when mounted on the vehicle.

[0044] The "circumferential groove" refers to a groove that continuously extends in the tire circumferential direction and has a width of 7.0 mm or more on the tread surface 1.

[0045] The "widthwise groove" refers to a groove that extends in the tire width direction, neither one end nor both ends of which communicate with the above-mentioned circumferential groove, and which has a groove width when a normal load is applied to a tire in a normal state and the tire contacts the ground on a flat surface with a camber angle of 0 degrees.

[0046] The "land ratio R" is the ratio of the total contact area of the contact surface that contacts the ground to the total surface area of the tread surface in a state where it is assumed that all grooves are filled when a normal load is applied to a tire in a normal state and the tire contacts the ground on a flat surface with a camber angle of 0 degrees. Here, all grooves include grooves that do not correspond to the above-mentioned circumferential grooves and widthwise grooves (for example, grooves that continuously extend in the tire circumferential direction and have a width of less than 7.0 mm on the tread surface, grooves that extend in the tire width direction and cross the land portion and both ends of which communicate with the circumferential groove, etc.).

[0047] The "area ratio of widthwise grooves in the shoulder land portion" refers to the total area of all grooves that cross the land portion with respect to the total area of the shoulder land portion. The "groove area ratio in the center land portion" refers to the total area of all grooves that cross the land portion with respect to the total area of the center land portion.

[0048] The "groove depth of the circumferential groove" is obtained by the distance between the tread surface and the extension line of the deepest part of the groove bottom of the circumferential groove. When there are a plurality of circumferential grooves, it is the distance between the tread surface and the extension line of the deepest part of the groove bottom of the circumferential groove having the deepest groove depth among the plurality of circumferential grooves.

[0049] The "oil content" includes the amount of oil contained in the oil-extended rubber.

[0050] <Measurement method> "The total area of the ground contact surface", "the total area of the shoulder land portions", "the total area of the center land portions", and the groove area crossing these land portions are values calculated based on the ground contact shape. The ground contact shape can be obtained by mounting the tire on a standard rim, maintaining the standard internal pressure, then, for example, applying ink to the tread portion, applying a standard load, pressing it vertically against cardboard, etc., and transferring the ink applied to the tread portion. Also, from the obtained ground contact shape, the sum of the areas of the shoulder land portions with all the grooves crossing the shoulder land portions filled is defined as the total area of the shoulder land portions, and the sum of the areas of the center land portions with all the grooves crossing the center land portions filled is defined as the total area of the center land portions.

[0051] "30°C tanδ" is the loss tangent measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%. The sample for loss tangent measurement is a vulcanized rubber composition with a length of 20 mm × a width of 4 mm × a thickness of 1 mm. When produced by cutting from a tire, it is cut from the tread portion of the tire such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction.

[0052] "30°C E*" is the complex elastic modulus (MPa) measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%. The sample for complex elastic modulus measurement is produced in the same manner as in the case of 30°C tanδ.

[0053] "tanδA" can be obtained as the average value of eight numerical values obtained by measuring tanδ under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25% at each temperature in 5°C increments from -15°C to 20°C. The sample for tanδA measurement is produced in the same manner as in the case of 30°C tanδ.

[0054] The "glass transition temperature (Tg) of the rubber composition" is determined as the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve, by measuring the temperature distribution curve of tanδ under the conditions of using an Iplexer series manufactured by GABO, a frequency of 10 Hz, an initial strain of 0.1%, a dynamic strain amplitude of ±0.25%, and a heating rate of 3°C / min. The sample for Tg measurement is prepared in the same manner as in the case of 30°C tanδ.

[0055] The "styrene content" is 1 a value calculated by 1H-NMR measurement and is applicable to rubber components having repeating units derived from styrene such as SBR. The "vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017 and is applicable to rubber components having repeating units derived from butadiene such as SBR and BR. The "cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017 and is applicable to rubber components having repeating units derived from butadiene such as BR.

[0056] The "weight average molecular weight (Mw)" can be determined by standard polystyrene conversion based on the measured values by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation). It is applicable to, for example, SBR, BR, etc.

[0057] The "average primary particle diameter of carbon black" can be determined by observing with a transmission or scanning electron microscope and measuring 400 or more primary particles of carbon black observed in the field of view and taking the average. The "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017. The "oil absorption amount of carbon black (DBP oil absorption amount (OAN))" is measured in accordance with JIS K 6217-4:2017.

[0058] The "N2SA of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0059] The "softening point of the resin component" is the temperature at which the sphere drops when measured with a ring and ball softening point measuring device for the softening point defined in JIS K 6220-1:2015 7.7.

[0060] The manufacturing procedure of the tire which is one embodiment of the present disclosure will be described in detail below. However, the following description is an exemplification for explaining the present disclosure, and is not intended to limit the technical scope of the present disclosure only to this description range. In this specification, when indicating a numerical range using "~", it shall include the numerical values at both ends thereof.

[0061] <Tire> FIG. 1 is a schematic view of the contact surface when the tread is pressed against a plane. A tread pattern is formed on the tread surface 1 constituting the tire according to the present disclosure.

[0062] In FIG. 1, the tread has a plurality of circumferential grooves 4. The circumferential grooves 4 extend linearly along the circumferential direction C, but are not limited to such a mode. For example, they may extend in a wavy, sine wave, or zigzag shape along the circumferential direction. In FIG. 1, three circumferential grooves 4 are provided, but in the present disclosure, the number of circumferential grooves is not particularly limited, and may be, for example, 2 to 5.

[0063] The shoulder land portions 3 are a pair of land portions formed between the circumferential grooves 4 and the tread end Te. The center land portion 2 is a land portion formed between the pair of shoulder land portions 3. In FIG. 1, two center land portions 2 are provided, but the number of center land portions is not particularly limited, and may be, for example, 1 to 5.

[0064] At least one of the land portions has a widthwise groove whose one or both ends do not communicate with the circumferential groove 4, and it is preferable that both ends have widthwise grooves that do not communicate with the circumferential groove 4. In FIG. 1, the shoulder land portion 3 is provided with a widthwise groove 8 whose one end communicates with the circumferential groove 4, and widthwise grooves 5 and 6 whose both ends do not communicate with the circumferential groove. Further, the center land portion 2 is provided with a widthwise groove 7 whose one end communicates with the circumferential groove 4, and a groove 9 that extends in the tire width direction, crosses the center land portion 2, and whose both ends communicate with the circumferential groove, but is not limited to such a mode.

[0065] In the tire of the present disclosure, the land ratio R on the ground contact surface of the tread portion is 0.50 or more, preferably 0.52 or more, more preferably 0.55 or more, still more preferably 0.57 or more, and particularly preferably 0.60 or more. When the land ratio R is less than 0.50, it is considered that the deformation of the tread portion increases and the grip performance decreases. Further, due to the decrease in the ground contact area, the heat generation property of the tread surface at the initial stage of running is reduced, and the initial grip performance and wear resistance tend to decrease. On the other hand, the land ratio R is 0.80 or less, preferably 0.77 or less, more preferably 0.75 or less, still more preferably 0.72 or less, and particularly preferably 0.70 or less. When the land ratio R exceeds 0.80, the rubber of the tread portion cannot be sufficiently deformed, and heat generation is less likely to occur, so the grip performance tends to decrease.

[0066] The ratio of the total area of the circumferential grooves to the ground contact area of the tread portion is preferably 0.12 or more, more preferably 0.14 or more, and still more preferably 0.16 or more. Further, the ratio of the total area of the circumferential grooves to the ground contact area of the tread portion is preferably 0.28 or less, more preferably 0.26 or less, and still more preferably 0.24 or less.

[0067] The ratio of the total area of the grooves in the width direction to the contact area of the tread portion is preferably 0.08 or more, more preferably 0.10 or more, and even more preferably 0.12 or more. Further, the ratio of the total area of the grooves in the width direction and the sipes 22, 23 to the contact area of the tread portion is preferably 0.20 or less, more preferably 0.18 or less, and even more preferably 0.16 or less.

[0068] The ratio of the total area of the center land portion 2 to the contact area of the tread portion is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more. By setting the ratio of the total area of the center land portion to the area of the entire land portion within the above range, the volume of the center land portion can be increased and the land portion rigidity can be increased. Therefore, it is considered that the rubber can maintain an appropriate hardness against heat generation caused by the edge component, and it becomes easier to decelerate during braking. Further, from the viewpoint of the effects of the present disclosure, the ratio of the total area of the center land portion 2 to the area of the entire land portion is preferably 0.65 or less, more preferably 0.60 or less, and even more preferably 0.55 or less.

[0069] In the present disclosure, the tread portion has at least one rubber layer. The tread portion of the present disclosure may be a tread composed of a single rubber layer, or may be a tread portion having a rubber layer (cap rubber layer) whose outer surface constitutes the tread surface 1 and one or more rubber layers existing between the cap rubber layer and the belt layer. The thickness of the cap rubber layer with respect to the total thickness of the entire tread portion can be, for example, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more.

[0070] In the present disclosure, the total thickness of the tread portion is preferably 5.0 mm or more, more preferably 5.5 mm or more, even more preferably 6.0 mm or more, and particularly preferably 6.5 mm or more. Further, the total thickness of the tread portion is preferably 10.0 mm or less, more preferably 9.5 mm or less, even more preferably 9.0 mm or less, and particularly preferably 8.5 mm or less. Note that the total thickness of the tread portion in the present disclosure means the total thickness of the rubber layers constituting the tread portion, and is obtained by the shortest distance from the tread surface 1 to the belt layer.

[0071] The groove depth at the deepest part of the circumferential groove 4 is preferably 20% or more of the thickness of the entire tread portion, more preferably 40% or more, even more preferably 50% or more, and particularly preferably 60% or more. The groove depth at the deepest part of the circumferential groove 4 is preferably 95% or less of the thickness of the entire tread portion, more preferably 90% or less, even more preferably 85% or less, and particularly preferably 80% or less.

[0072] Fig. 2 is an enlarged cross-sectional view showing a portion of a tire tread, in which the up-down direction is the tire radial direction, the left-right direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

[0073] In the present disclosure, it is preferable that the tire width direction length of at least one land portion gradually increases from the outer side toward the inner side in the tire radial direction. This makes it possible for the land portion to be easily deformed and for the entire land portion to be easily heated. In addition, since the area of the bottom surface of the land portion is increased, the reaction force can also be increased when a steering angle is applied. From this, it is considered that a large reaction force can be generated against the grip generated on the tread surface 1, and the initial grip performance and the peak grip performance can be improved. In addition, the groove wall 15 of the circumferential groove of the present disclosure extends linearly from the outer side toward the inner side in the tire radial direction, but is not limited to such an embodiment, and may extend, for example, in a curved or stepped shape.

[0074] The groove width L at 95% of the deepest part of the groove bottom of the circumferential groove 4 relative to the groove width L0 on the tread surface of the circumferential groove 4 located at the outermost side when mounted on the vehicle. 95 Ratio (L 95 From the viewpoint of the effects of the present disclosure, L is preferably 0.10 or more, more preferably 0.15 or more, even more preferably 0.20 or more, still more preferably 0.25 or more, and particularly preferably 0.30 or more. 95 / L0 is preferably 0.60 or less, more preferably 0.55 or less, still more preferably 0.50 or less, still more preferably 0.45 or less, and particularly preferably 0.40 or less. In FIG. 2, illustration of each rubber layer is omitted.

[0075] From the viewpoint of grip performance, tanδA of the rubber composition of the present disclosure is 0.40 or more, preferably 0.41 or more, more preferably 0.43 or more, still more preferably 0.45 or more, and particularly preferably 0.47 or more. Further, from the viewpoint of blow resistance performance, tanδA of the rubber composition is 0.60 or less, preferably 0.58 or less, more preferably 0.56 or less, still more preferably 0.54 or less, and particularly preferably 0.52 or less.

[0076] From the viewpoint of grip performance, 30°C tanδ of the rubber composition of the present disclosure is preferably 0.32 or more, more preferably 0.35 or more, still more preferably 0.37 or more, and particularly preferably 0.40 or more. Further, from the viewpoint of blow resistance performance, it is preferably 0.55 or less, more preferably 0.53 or less, still more preferably 0.50 or less, and particularly preferably 0.48 or less.

[0077] From the viewpoint of grip performance, 30°C E* of the rubber composition of the present disclosure is preferably 60 MPa or less, more preferably 56 MPa or less, still more preferably 53 MPa or less, still more preferably 50 MPa or less, and particularly preferably 48 MPa or less. Further, from the viewpoint of handling stability performance, it is preferably 8 MPa or more, more preferably 9 MPa or more, still more preferably 10 MPa or more, still more preferably 12 MPa or more, still more preferably 15 MPa or more, and particularly preferably 20 MPa or more.

[0078] The Tg of the rubber composition of the present disclosure is preferably -25°C or higher, more preferably -20°C or higher, and still more preferably -15°C or higher. By setting the Tg of the rubber composition within the above range, it is possible to increase the energy loss corresponding to the frequency of vibration generated during rolling during normal driving. The upper limit value of Tg of the rubber composition is not particularly limited, but is preferably 20°C or lower, more preferably 15°C or lower, and still more preferably 10°C or lower.

[0079] Incidentally, tanδT, tanδA, 30°C tanδ, 30°C E*, and Tg of the rubber composition of the present disclosure can be appropriately adjusted according to the types and blending amounts of the rubber component, filler, softening agent, etc. described later.

[0080] The product of tanδA represented by the above formula (1) and the land ratio R is 0.20 or more, preferably 0.21 or more, more preferably 0.24 or more, further preferably 0.27 or more, and particularly preferably 0.29 or more. By setting the product of tanδA and the land ratio R within the above range, the tread rubber can secure good rigidity and contact area, and the heat generation property is also improved, so it is considered that the grip performance can be further improved. Further, from the viewpoint of the effects of the present disclosure, the product of tanδT and the land ratio R is 0.48 or less, preferably 0.45 or less, more preferably 0.42 or less, further preferably 0.39 or less, and particularly preferably 0.36 or less.

[0081] The L represented by the above formula (2) 95 The ratio of tanδA to L 95 / L0 (tanδA / (L 95 / L0)) is preferably 0.67 or more, more preferably 0.78 or more, further preferably 1.00 or more, further preferably 1.10 or more, further preferably 1.20 or more, and particularly preferably 1.29 or more. By setting the product of tanδA and the land ratio R within the above range, the tread rubber can secure good rigidity and contact area, and the heat generation property is also improved, so it is considered that the grip performance can be further improved. Further, from the viewpoint of the effects of the present disclosure, tanδA / (L

[0082] [Rubber composition] The tire of the present disclosure can more effectively improve the initial grip performance and peak grip performance by the cooperation of the above-described tread pattern and the above physical properties of the rubber composition. The rubber composition of the present disclosure is used for at least one rubber layer constituting the tread portion. Further, in the case of a tire provided with a tread portion having two or more rubber layers, the rubber composition of the present disclosure is preferably used for any rubber layer other than the innermost layer adjacent to the outer side in the tire radial direction of the belt layer; more preferably used for a rubber layer (cap rubber layer) at least the outer surface of which constitutes the tread surface 1.

[0083] <Rubber component> In the rubber composition of the present disclosure, a diene rubber is preferably used as the rubber component. From the viewpoint of the effects of the present disclosure, the content of the diene rubber in the rubber component is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Further, the rubber component may be composed only of a diene rubber.

[0084] Examples of the diene rubber include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and the like. These diene rubbers may be used alone or in combination of two or more. Among them, it is preferable to contain at least one selected from the group consisting of isoprene rubber, BR, and SBR; more preferably contain SBR; still more preferably contain SBR and at least one of isoprene rubber and BR. Further, the rubber component may be composed only of SBR, or the rubber component may be composed only of SBR and BR.

[0085] (Isoprene rubber) Examples of isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. As NR, for example, those commonly used in the tire industry such as SIR20, RSS#3, TSR20, etc. can be used. These isoprene rubbers may be used alone or in combination of two or more.

[0086] When containing isoprene rubber, the content in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less from the viewpoint of peak grip performance. The lower limit of the content is not particularly limited, but from the viewpoint of initial grip performance, it can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more.

[0087] (BR) BR is not particularly limited. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used alone or in combination of two or more. The cis content of BR is measured by the above measurement method.

[0088] As high-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the low-temperature characteristics and abrasion resistance can be improved. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, still more preferably 97 mol% or more, and particularly preferably 98 mol% or more. The cis content of BR is measured by the above measurement method.

[0089] The weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more from the viewpoint of wear resistance performance. Further, from the viewpoints of crosslinking uniformity and the like, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. The Mw of BR is measured by the above measurement method.

[0090] The content in the rubber component when containing BR is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more from the viewpoint of initial grip performance. Further, the content of BR is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 15% by mass or less.

[0091] (SBR) There is no particular limitation on SBR, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR, etc.). Examples of modified SBR include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Among them, S-SBR and modified SBR are preferred. Further, hydrogenated products of these SBRs (hydrogenated SBR) etc. can also be used.

[0092] The SBRs listed above may be used alone or in combination of two or more. As the SBRs listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. can be used.

[0093] From the viewpoints of peak grip performance and abrasion resistance performance, the styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more. Also, from the viewpoints of temperature dependence of grip performance and blow resistance performance, it is preferably 60% by mass or less, more preferably 55% by mass or less, and still more preferably 50% by mass or less. The styrene content of SBR is measured by the above measurement method.

[0094] From the viewpoints of ensuring reactivity with silica, peak grip performance, and abrasion resistance performance, the vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and still more preferably 20 mol% or more. Also, from the viewpoints of preventing an increase in temperature dependence, elongation at break, and abrasion resistance performance, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and still more preferably 60 mol% or less. The vinyl content of SBR is measured by the above measurement method.

[0095] From the viewpoint of peak grip performance, the weight average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more. Also, from the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and still more preferably 1,500,000 or less. The weight average molecular weight of SBR is measured by the above measurement method.

[0096] From the viewpoint of the effects of the present disclosure, the content in the rubber component when containing SBR is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more. Also, the upper limit value of the content of SBR is not particularly limited, and for example, it can be 100% by mass, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less.

[0097] (Other rubber components) The rubber component may contain other rubber components other than diene rubber as long as the effects of the present disclosure are not affected. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used. For example, butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. In addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0098] <Filler> The rubber composition of the present disclosure preferably contains carbon black and / or silica as a filler, and more preferably contains carbon black. Further, the filler may be a filler consisting only of carbon black and silica, or a filler consisting only of carbon black.

[0099] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0100] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 100 m 2 / g or more, more preferably 120 m 2 / g or more, still more preferably 140 m 2 / g or more, particularly preferably 150 m 2 / g or more, from the viewpoint of ensuring reinforcing properties and peak grip performance. Also, from the viewpoint of dispersibility, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2Less than / g is more preferable. The N2SA of silica is measured by the above-mentioned measurement method.

[0101] From the viewpoint of the effects of the present disclosure, the content of silica based on 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and particularly preferably 60 parts by mass or more. Further, from the viewpoint of reducing the specific gravity of the rubber and achieving weight reduction, 130 parts by mass or less is preferable, 120 parts by mass or less is more preferable, and 110 parts by mass or less is still more preferable.

[0102] (Carbon black) The carbon black is not particularly limited, and for example, those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0103] From the viewpoints of reinforcing property and peak grip performance, the average primary particle diameter of the carbon black is preferably 40 nm or less, more preferably 35 nm or less, still more preferably 30 nm or less, further preferably 25 nm or less, still further preferably 22 nm or less, and particularly preferably 20 nm or less. Also, from the viewpoint of dispersibility, 10 nm or more is preferable, 12 nm or more is more preferable, and 15 nm or more is still more preferable. The average primary particle diameter of the carbon black is measured by the above-mentioned measurement method.

[0104] From the viewpoints of reinforcing property and peak grip performance, the nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 50 m 2 / g or more, more preferably 70 m 2 / g or more, still more preferably 100 m 2 / g or more, and particularly preferably 120 m 2 / g or more. Also, from the viewpoint of dispersibility, 250 m 2 / g or less is preferable, and 220 m 2 / g or less is more preferable. The N2SA of the carbon black is measured by the above-mentioned measurement method.

[0105] The oil absorption amount (DBP oil absorption amount (OAN)) of carbon black is preferably 85 mL / 100 g or more, more preferably 90 mL / 100 g or more, and still more preferably 100 mL / 100 g or more from the viewpoints of reinforcement and peak grip performance. Further, from the viewpoint of grip performance, the OAN is preferably 250 mL / 100 g or less, more preferably 225 mL / 100 g or less, and still more preferably 200 mL / 100 g or less. The OAN of carbon black is measured by the above measurement method.

[0106] The content of carbon black with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more from the viewpoints of weather resistance and reinforcement. Further, from the viewpoint of low fuel consumption performance, it is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, still more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less.

[0107] (Other fillers) As fillers other than silica and carbon black, those generally used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., can be blended.

[0108] The total content of the fillers with respect to 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, still more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more from the viewpoints of reinforcement and grip performance. Further, from the viewpoint of dispersibility, it is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, still more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less.

[0109] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent conventionally used in combination with silica can be used. For example, mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide; thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane, vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane; and the like. Among them, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As the silane coupling agent, for example, those commercially available from Momentive and other companies can be used. These silane coupling agents may be used alone or in combination of two or more.

[0110] When a silane coupling agent is contained, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 2.0 part by mass or more, and particularly preferably 4.0 part by mass or more from the viewpoint of enhancing the dispersibility of silica. Further, from the viewpoint of preventing a decrease in abrasion resistance performance, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

[0111] The content of the silane coupling agent with respect to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 part by mass or more, and still more preferably 5.0 part by mass or more from the viewpoint of enhancing the dispersibility of silica. Further, from the viewpoints of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

[0112] <Softening agent> The rubber composition according to the present disclosure preferably contains a softening agent. Examples of the softening agent include a resin component, an oil, a liquid rubber, an ester plasticizer, and the like.

[0113] (Resin component) The resin component is not particularly limited, and examples thereof include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry. These resin components may be used alone or in combination of two or more.

[0114] In the present specification, the "C5-based petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, and isoprene. As the C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0115] As used herein, the term "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples of the aromatic petroleum resin, for example, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin are preferably used. As the aromatic vinyl resin, due to economic reasons, ease of processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from companies such as Kraton Corporation and Eastman Chemical Company can be used.

[0116] As used herein, the term "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, which may be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Company, etc. can be used.

[0117] Examples of terpene resins include polyterpene resins composed of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; aromatic modified terpene resins using the terpene compounds and aromatic compounds as raw materials; terpene phenol resins using terpene compounds and phenolic compounds as raw materials; and those obtained by subjecting these terpene resins to a hydrogenation treatment (hydrogenated terpene resins). Examples of the aromatic compounds used as raw materials for the aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of the phenolic compounds used as raw materials for the terpene phenol resins include phenol, bisphenol A, cresol, and xylenol.

[0118] The rosin-based resin is not particularly limited, and examples thereof include natural resin rosin, and rosin-modified resins obtained by modifying the natural resin rosin by hydrogenation, disproportionation, dimerization, esterification, etc.

[0119] The phenolic resin is not particularly limited, and examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc.

[0120] From the viewpoint of grip performance, the softening point of the resin component is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. Further, from the viewpoints of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the resin component is measured by the above measurement method.

[0121] From the viewpoint of peak grip performance, the content of the resin component with respect to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more. Further, from the viewpoint of processability, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0122] (Oil) Examples of the oil include process oil, vegetable oil, animal oil, etc. Examples of the process oil include paraffinic process oil, naphthenic process oil, aromatic process oil, etc. Further, a process oil having a low content of polycyclic aromatic compound (PCA) can also be used for environmental measures. Examples of the low-PCA-content process oil include mildly extracted solvent-solvate (MES), treated distillate aromatic extract (TDAE), heavy naphthenic oil, etc.

[0123] When contained, the content relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more from the viewpoint of processability. Further, from the viewpoint of abrasion resistance performance, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less.

[0124] (Liquid rubber) The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25 °C). For example, liquid butadiene rubber (liquid BR), liquid styrene-butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene-isoprene rubber (liquid SIR), liquid farnesene rubber, etc. can be mentioned. These liquid rubbers may be used alone or in combination of two or more.

[0125] When contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more. Further, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less.

[0126] (Ester plasticizer) Examples of the ester plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. These ester plasticizers may be used alone or in combination of two or more.

[0127] When contained, the content of the ester plasticizer relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more from the viewpoint of initial grip performance. Further, from the viewpoint of peak grip performance, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0128] The total content of the resin component and the ester plasticizer relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. Also, the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. By setting the total content of the resin component and the ester plasticizer within the above range, the initial grip performance and the peak grip performance can be improved in a well-balanced manner.

[0129] The content of the softening agent relative to 100 parts by mass of the rubber component (when a plurality of softening agents are used in combination, the total amount of all) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more from the viewpoint of peak grip performance. Also, from the viewpoint of processability, it is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0130] <Other compounding agents> In addition to the above components, the rubber composition according to the present disclosure may appropriately contain compounding agents generally used in the conventional tire industry, such as wax, processing aids, anti-aging agents, stearic acid, zinc oxide, crosslinking agents, vulcanization accelerators, and the like.

[0131] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0132] The anti-aging agent is not particularly limited. Examples include anti-aging agents such as amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and metal carbamates. P-phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These anti-aging agents may be used alone or in combination of two or more.

[0133] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Also, from the viewpoints of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0134] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0135] When zinc oxide is contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Further, from the viewpoint of abrasion resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0136] As the crosslinking agent, sulfur is preferably used. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0137] When sulfur is contained, the content relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and still more preferably 0.5 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction. Further, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. In addition, when oil-containing sulfur is used as the crosslinking agent, the content of the vulcanizing agent is the total content of the pure sulfur component contained in the oil-containing sulfur.

[0138] As a crosslinking agent other than sulfur, known organic crosslinking agents can also be used. When an organic crosslinking agent is blended, the distance between crosslinking points becomes longer compared to crosslinking with sulfur, and it becomes possible to generate more energy loss, and good peak grip performance can be obtained.

[0139] The organic crosslinking agent is not particularly limited as long as it can form a crosslinking chain other than a polysulfide bond. For example, alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiocarbonate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, dicumyl peroxide, etc. can be mentioned, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is preferred. These organic crosslinking agents can be those commercially available from Tago Chemical Industry Co., Ltd., Rancess Co., Ltd., Flexsys Co., etc.

[0140] When an organic crosslinking agent is contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more. Also, the content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 6 parts by mass or less.

[0141] Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, guanidine-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, caprolactam disulfide, and the like. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint that a desired effect can be more suitably obtained, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, thiuram-based vulcanization accelerators, and caprolactam disulfide are preferable, and one or more vulcanization accelerators selected from the group consisting of dithiocarbamate-based vulcanization accelerators and thiuram-based vulcanization accelerators are more preferable.

[0142] Examples of the sulfenamide-based vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and the like. Among them, TBBS and CBS are preferable.

[0143] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole (MBT) or its salt, di-2-benzothiazolyldisulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and the like. Among them, MBTS and MBT are preferable, and MBTS is more preferable.

[0144] Examples of thiuram vulcanization accelerators include tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like. Among them, TOT-N and TMTD are preferred, and TOT-N is more preferred.

[0145] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, DPG is preferred.

[0146] Examples of dithiocarbamate vulcanization accelerators include piperidinium pentamethylenedithiocarbamate (PPDC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), zinc dibenzyldithiocarbamate (ZDBzC), zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), zinc N-pentamethylenedithiocarbamate (ZnPDC), sodium dibutyldithiocarbamate (NaBDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate (FeMDC), tellurium diethyldithiocarbamate (TeEDC), and the like. Among them, ZnBDC and ZDBzC are preferred.

[0147] Examples of the caprolactam disulfide include N,N'-di(δ-caprolactam) disulfide, N,N'-di(ε-caprolactam) disulfide, N,N'-di(3-methyl-δ-caprolactam) disulfide, N,N'-di(3-ethyl-ε-caprolactam) disulfide, N,N'-di(δ-methoxy-ε-caprolactam) disulfide, N,N'-di(3-chloro-ε-caprolactam) disulfide, N,N'-di(δ-nitro-ε-caprolactam) disulfide, N,N'-di(3-amino-ε-caprolactam) disulfide, and the like. Among them, N,N'-di(ε-caprolactam) disulfide is preferable.

[0148] When containing a vulcanization accelerator, the content thereof with respect to 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and still more preferably 2.0 parts by mass or more. Also, the content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0149] <Manufacture> The rubber composition according to the present disclosure can be produced by a known method. For example, it can be produced by kneading the above-mentioned respective components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0150] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Further, the base kneading process can be divided into a plurality of processes if desired.

[0151] Although the kneading conditions are not particularly limited, for example, in the base kneading step, knead at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading step, knead at 70 to 110°C for 1 to 5 minutes. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be mentioned.

[0152] The tire of the present disclosure provided with a tread composed of the rubber composition can be manufactured by a normal method. That is, an unvulcanized rubber composition in which each of the above components is blended with the rubber component as needed is extruded according to the shape of at least one rubber layer constituting the tread, bonded together with other tire members on a tire molding machine, and molded by a normal method to form an unvulcanized tire, and this unvulcanized tire is heated and pressurized in a vulcanizer to manufacture a tire. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be mentioned.

[0153] <Use> The tire of the present disclosure can be a general-purpose tire such as a passenger car tire, a truck / bus tire, or a motorcycle tire, or a racing tire. In addition, a passenger car tire is a tire assumed to be mounted on a four-wheeled automobile, and refers to one with a maximum load capacity of 1000 kg or less. Further, the tire of the present disclosure can be used for all-season tires, summer tires, winter tires such as studless tires, etc.

Examples

[0154] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to these examples only.

[0155] Hereinafter, various chemicals used in the examples and comparative examples are collectively shown. NR:TSR20 SBR: HP755B manufactured by JSR Corporation (S-SBR, styrene content: 37% by mass, vinyl content: 37 mol%, containing 37.5 parts by weight of oil per 100 parts by weight of rubber component) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97 mol%, Mw: 440,000) Carbon black 1: Show Black N330 manufactured by Cabot Japan Ltd. (N2SA: 75 m 2 / g, DBP absorption oil amount: 102 mL / 100 g, average primary particle diameter: 28 nm) Carbon black 2: Seast 9 (SAF, N2SA: 142 m 2 / g, DBP absorption oil amount: 115 mL / 100 g, average primary particle diameter: 19 nm) Silica: ZEOSIL 1165MP manufactured by Rhodia (N2SA: 160 m 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa Resin component 1: Petro Tack 100V (C5C9-based petroleum resin, softening point: 96°C) manufactured by Tosoh Corporation Resin component 2: YS Resin TO125 (terpene styrene resin, softening point: 125°C) manufactured by Yasuhara Chemical Co., Ltd. Ester plasticizer: DOS (bis(2-ethylhexyl) sebacate) manufactured by Ohyagi Chemical Industry Co., Ltd. Liquid rubber: L-SBR-820 (liquid SBR) manufactured by Kuraray Co., Ltd. Oil: VivaTec500 (TDAE oil) manufactured by H&R Co., Ltd. Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Bead Stearic Acid Tsubaki manufactured by NOF Corporation Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Wax: Sunoc N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Sulfur: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. Organic crosslinking agent: VP KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Rancess Co., Ltd. Vulcanization accelerator 1: Sanseller CM-G (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noceller ZTC (zinc dibenzyldithiocarbamate (ZDBzC)) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Vulcanization accelerator 3: Noceller TOT-N (tetrakis(2-ethylhexyl)thiuram disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Vulcanization accelerator 4: Renogran CLD-80 (N,N'-di(ε-caprolactam)disulfide) manufactured by Rhein Chemie

[0156] (Examples and Comparative Examples) According to the compounding formulations shown in Table 1 and Table 2, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators were kneaded for 1 to 10 minutes until the discharge temperature reached 150 to 160 °C to obtain a kneaded product. Next, using a twin-screw open roll, sulfur and vulcanization accelerators were added to the obtained kneaded product and kneaded for 4 minutes until the temperature reached 105 °C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was extruded and molded into the shape of a tread cap rubber layer (thickness: 5.5 mm) using an extruder equipped with a die of a predetermined shape, and laminated together with an intermediate rubber layer (thickness: 1.5 mm) interposed between the cap rubber layer and the belt layer and other tire members to produce an unvulcanized tire, which was press-vulcanized at 170 °C for 12 minutes to obtain each test tire (size: 205 / 55R15, rim: 16 × 6.5J, internal pressure: 230 kPa) shown in Table 3 and Table 4. The groove depth (deepest part) of the circumferential groove was set to 5.0 mm. Table 3 shows passenger car tires and Table 4 shows race tires.

[0157] (Measurement of tanδA and Tg of the rubber composition) Each vulcanized rubber test piece was cut out from each rubber layer of the tread part of each test tire to have a length of 20 mm × width of 4 mm × thickness of 1 mm, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction. For each rubber test piece, using an Iplexer series manufactured by GABO, the loss tangent tanδ was measured at each temperature in 5°C increments from -15°C to 20°C under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25%. Then, the average value of the obtained 8 numerical values was taken as tanδA. Also, the temperature distribution curve of tanδ was measured under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, a dynamic strain amplitude of ±0.25%, and a heating rate of 3°C / min, and the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve was taken as the glass transition temperature (Tg). The results are shown in Tables 1 and 2.

[0158] <Measurement of tanδ at 30°C and E* at 30°C> Each vulcanized rubber test piece was cut out from each rubber layer of the tread part of each test tire to have a length of 20 mm × width of 4 mm × thickness of 1 mm, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction. For each rubber test piece, using an Iplexer series manufactured by GABO, tanδ and the complex elastic modulus (E*) were measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%. The results are shown in Tables 1 and 2.

[0159] <Initial grip performance> The test tires were mounted on all four wheels of a domestic FR car (2000 cc) and 10 laps of on-road driving were performed on a test course on a dry asphalt road surface. The test driver subjectively evaluated the stability of the control during steering in the second lap. The evaluation was performed using integer values from 1 to 10, and based on the evaluation criteria where a higher score indicates better stability of the control during steering, the total score of 10 test drivers was calculated. The total score of the reference comparative example (Comparative Example 1 in Table 3 and Comparative Example 12 in Table 4) was converted to a reference value (100), and the evaluation results of each test tire were indexed to be proportional to the total score for display. A larger numerical value indicates higher initial grip performance.

[0160] <Peak grip performance> The test tires were mounted on all wheels of a domestic FR car (2000 cc), and the vehicle was driven on a test course on a dry asphalt road surface for 10 laps. During this time, the test driver subjectively evaluated the stability of the control during steering for the best lap and the final lap. The evaluation was conducted on an integer scale from 1 to 10, and based on the evaluation criteria that the higher the score, the better the stability of the control during steering, the total score of 10 test drivers was calculated. The total score of the reference comparison example (Comparative Example 1 in Table 3 and Comparative Example 12 in Table 4) was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed in proportion to the total score. A larger numerical value indicates that the decrease in grip performance during driving on a dry road surface is smaller, and stable grip performance during driving can be obtained well.

[0161] Note that the comprehensive performance of the initial grip performance and the peak grip performance (the sum of the initial grip performance index and the peak grip performance index) has a performance target value of over 200.

[0162]

Table 1

[0163]

Table 2

[0164]

Table 3

[0165]

Table 4

[0166] From the results of Table 3 and Table 4, it can be seen that the tires of the present disclosure with the land ratio at the ground contact surface of the tread portion and the average value of the loss tangent tanδ in a specific temperature range within a predetermined range have improved comprehensive performance of the initial grip performance and the peak grip performance on a dry road surface.

[0167] <Embodiment> Examples of embodiments of the present disclosure are shown below.

[0168] 〔1〕A tire having a tread portion, wherein the tread portion has two or more circumferential grooves continuously extending in the tire circumferential direction, a pair of shoulder land portions partitioned by the circumferential grooves and a ground contact end, a center land portion located between the pair of shoulder land portions, and a width direction groove, and a land ratio R on the ground contact surface of the tread portion is 0.50 to 0.8 at 0 Yes, the tread portion has at least one rubber layer made of a rubber composition containing a rubber component, and an average value tanδA of loss tangent tanδ of the rubber composition at -15°C to 20°C measured under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25% is 0.40 to 0.60. 〔2〕The tire according to 〔1〕 above, wherein tanδA and the land ratio R satisfy the following formula (1). Formula (1) 0.21 ≦ tanδA × R ≦ 0.45 〔3〕The tire according to 〔1〕 or 〔2〕 above, wherein the rubber component contains at least one of an isoprene-based rubber and a butadiene rubber. 〔4〕The tire according to any one of 〔1〕 to 〔3〕 above, wherein the tire width direction length of at least one of the land portions gradually increases from the outer side to the inner side in the tire radial direction. 〔5〕The groove width on the tread surface of the circumferential groove located on the outermost side when mounted on a vehicle is L0, and the groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove located on the outermost side when mounted on a vehicle is L 95 When it is set as 95 The tire according to any one of 〔1〕 to 〔4〕 above, wherein L / L0 is 0.10 to 0.50. 〔6〕The tire according to the above 95 described, wherein tanδA and L / L0 satisfy the following formula (2). 〔5〕 described tire. Formula (2) tanδA / (L 95 / L0) ≧ 1.20 〔7〕The tire according to any one of the above 〔1〕 to 〔6〕, wherein the rubber composition contains 5 to 50 parts by mass of a resin component and / or an ester plasticizer with respect to 100 parts by mass of the rubber component. 〔8〕The tire according to any one of the above 〔1〕 to 〔7〕, wherein the rubber composition contains 5 to 150 parts by mass of carbon black having an average primary particle diameter of 25 nm or less with respect to 100 parts by mass of the rubber component. 〔9〕The tire according to any one of the above 〔1〕 to 〔8〕, wherein the rubber composition contains 1 to 10 parts by mass of an organic crosslinking agent with respect to 100 parts by mass of the rubber component. 〔10〕The tire according to any one of the above 〔1〕 to 〔9〕, wherein tanδ (tanδ at 30°C) of the rubber composition is 0.35 or more. 〔11〕The tire according to any one of the above 〔1〕 to 〔10〕, wherein the complex elastic modulus (E* at 30°C) of the rubber composition is 50 MPa or less. 〔12〕The tire according to any one of the above 〔1〕 to 〔11〕, wherein the glass transition temperature of the rubber composition is -25°C or more. 〔13〕The tire according to any one of the above 〔1〕 to 〔12〕, wherein the ratio of the total area of the circumferential grooves to the contact area of the tread portion is 0.12 to 0.28, and the ratio of the total area of the widthwise grooves to the contact area of the tread portion is 0.08 to 0.20. 〔14〕The tire according to any one of the above 〔1〕 to 〔13〕, wherein the ratio of the total area of the center land portions to the contact area of the tread portion is 0.30 to 0.65. 〔15〕The tire according to any one of the above 〔1〕 to 〔14〕, wherein the area ratio of the widthwise grooves in the shoulder land portions is larger than the area ratio of the widthwise grooves in the center land portions.

Explanation of Signs

[0169] 1 Tread surface 2 Center land portion 3 Shoulder land portion 4 Circumferential groove 5, 6, 7, 8 Widthwise grooves 9 Groove with both ends communicating with the circumferential groove 15 Groove wall C Tire circumferential direction W Tire width direction CL Tire equator Te Tread edge Groove width at the tread surface of the circumferential groove L 95 Groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove

Claims

1. A tire having a tread portion, wherein the tread portion has two or more circumferential grooves continuously extending in the tire circumferential direction, a pair of shoulder land portions partitioned by the circumferential grooves and a ground contact end, a center land portion positioned between the pair of shoulder land portions, and a width direction groove; a land ratio R on the ground contact surface of the tread portion is 0.50 to 0.80; the tread portion has at least one rubber layer made of a rubber composition containing a rubber component; an average value tanδA of loss tangent tanδ of the rubber composition at -15°C to 20°C is 0.40 to 0.60; wherein the tanδA is obtained as an average value of eight numerical values obtained by measuring tanδ under the conditions of a frequency of 10 Hz, an initial strain of 0.1%, and a dynamic strain amplitude of ±0.25% at each temperature in 5°C increments from -15°C to 20°C. A tire

2. The tire according to claim 1, wherein tanδA and the land ratio R satisfy the following formula (1). Formula (1): 0.21 ≦ tanδA × R ≦ 0.45

3. The tire according to claim 1 or 2, wherein the rubber component contains at least one of an isoprene-based rubber and a butadiene rubber.

4. The tire according to any one of claims 1 to 3, wherein the tire width direction length of at least one land portion of the shoulder land portion and the center land portion gradually increases from the outer side to the inner side in the tire radial direction.

5. Let L be the groove width at the tread surface of the circumferential groove located at the outermost side when the tire is mounted on a vehicle. 0 Let L be the groove width at the 95% position of the deepest part of the groove bottom of the circumferential groove located at the outermost side when the tire is mounted on a vehicle. 95 When this is the case, 95 L 0 / L is 0.10 to 0.

50. The tire according to any one of claims 1 to 4.

6. tanδA and L 95 / L 0 The tire according to claim 5, wherein 95 / L 0 satisfies the following formula (2). Equation (2) tanδA / (L 95 / L 0 ) ≥ 1.20

7. The tire according to any one of claims 1 to 6, wherein the rubber composition contains 5 to 50 parts by mass of a resin component and / or an ester-based plasticizer with respect to 100 parts by mass of the rubber component.

8. The tire according to any one of claims 1 to 7, wherein the rubber composition contains 5 to 150 parts by mass of carbon black having an average primary particle diameter of 25 nm or less with respect to 100 parts by mass of the rubber component.

9. The tire according to any one of claims 1 to 8, wherein the rubber composition contains 1 to 10 parts by mass of an organic crosslinking agent with respect to 100 parts by mass of the rubber component.

10. tanδ (tanδ at 30°C) of the rubber composition at 30°C is 0.35 or more, wherein the tanδ of the rubber composition at 30°C is measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%. The tire according to any one of claims 1 to 9.

11. The complex elastic modulus (30°C E*) of the rubber composition at 30°C is 50 MPa or less, wherein the complex elastic modulus of the rubber composition at 30°C is measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%. The tire according to any one of claims 1 to 10.

12. The tire according to any one of claims 1 to 11, wherein the glass transition temperature of the rubber composition is -25°C or higher.

13. The ratio of the total area of the circumferential grooves to the contact area of the tread portion is 0.12 to 0.28, and the ratio of the total area of the widthwise grooves to the contact area of the tread portion is 0.08 to 0.

20. The tire according to any one of claims 1 to 12.

14. The ratio of the total area of the center land portions to the contact area of the tread portion is 0.30 to 0.

65. The tire according to any one of claims 1 to 13.

15. The tire according to any one of claims 1 to 14, wherein the area ratio of the widthwise grooves in the shoulder land portions is larger than the area ratio of the widthwise grooves in the center land portions.

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