JP6753219B2 - Golf ball - Google Patents

Description

The present invention relates to a golf ball. In particular, the present invention relates to a golf ball having dimples on its surface.

A golf ball has a large number of dimples on its surface. Dimples enhance the aerodynamics of a golf ball.

A golf ball having a minute protrusion or a minute dent together with a dimple has been proposed. These protrusions and dents can contribute to aerodynamic characteristics, spin performance, appearance, ease of manufacture, and the like.

Japanese Unexamined Patent Publication No. 2015-142599 discloses a golf ball having a paint layer having a large roughness. This roughness can be formed by blasting or the like. This paint layer enhances the aerodynamics of the golf ball.

JP-A-2015-142599

A golf ball hit by a golf club flies in the air. This golf ball falls and rolls on the ground. The golf ball comes into contact with the ground when falling and rolling. This contact may cause mud to adhere to the surface of the golf ball and stain the surface. When the golf ball is on the fairway or rough, the player cannot touch the golf ball. Therefore, the player cannot remove the dirt on the golf ball. On the green, the player can clean the golf ball. However, this removal work is troublesome. Dirt may not be sufficiently removed by work. Dirt may not be removed even if washed with water. Dirty golf balls are replaced. The exchange imposes a financial burden on the player.

Since the golf ball disclosed in JP-A-2015-142599 has a large roughness of the paint layer, mud easily adheres to the golf ball. The antifouling property of this golf ball is not sufficient. Even if this golf ball is washed with water, the mud is difficult to remove. The cleanability of this golf ball is not sufficient.

An object of the present invention is to provide a golf ball having excellent antifouling property and cleanability.

The golf ball according to the present invention includes a plurality of dimples and lands. The golf ball further comprises a large number of microprojections formed on the surface of the dimples and / or lands. The average pitch Pav of these microprojections is 100 μm or more.

Preferably, the average height Hav of the microprojections is 0.5 μm or more and 50 μm or less.

Preferably, the golf ball satisfies the following formula.
Lav> 0.5 ・ Tav
In this formula, Lav represents the average value of the distance L between the microprojection and other microprojections adjacent to the microprojection, and Tav represents the average value of the width T of the microprojection.

A golf ball can have multiple rows. Preferably, in each row, a plurality of microprojections are arranged at equal pitches.

A golf ball may have a body and a paint layer located outside the body. Preferably, the microprojections have a shape that reflects the surface shape of the body.

When the golf ball according to the present invention falls or rolls on the ground, mud may come into contact with the surface of the golf ball. Since mud flows as a flow path between the microprojections and the microprojections adjacent to the microprojections, the mud is unlikely to adhere to the golf ball. This golf ball is hard to get dirty.

Water also easily flows between the microprojections and the microprojections adjacent to them. Therefore, even if mud adheres to the surface, when it is washed with water, this water takes in dirt and flows. With this golf ball, dirt is easily removed.

FIG. 1 is a partially cutaway sectional view showing a golf ball according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the golf ball of FIG. FIG. 3 is an enlarged perspective view showing a part of the surface of the golf ball of FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the golf ball of FIG. FIG. 5 is a cross-sectional view taken along the line VV of FIG. FIG. 6 is an enlarged cross-sectional view showing a part of the golf ball of FIG.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

The golf ball 2 shown in FIG. 1 includes a spherical core 4, an intermediate layer 6 located outside the core 4, and a cover 8 located outside the intermediate layer 6. The core 4, the intermediate layer 6, and the cover 8 are included in the main body 10 of the golf ball 2. The golf ball 2 has a large number of dimples 12 on its surface. The portion of the surface of the golf ball 2 other than the dimples 12 is the land 14. Although not shown in FIG. 1, the golf ball 2 further has a paint layer described below. The paint layer is located on the outside of the main body 10. The main body 10 may have a one-piece structure. The main body 10 may have a two-piece structure, a four-piece structure, a five-piece structure, or the like.

The diameter of the golf ball 2 is preferably 40 mm or more and 45 mm or less. A diameter of 42.67 mm or more is particularly preferred from the perspective of meeting the standards of the United States Golf Association (USGA). From the viewpoint of suppressing air resistance, the diameter is more preferably 44 mm or less, and particularly preferably 42.80 mm or less. The diameter of the golf ball 2 according to the present embodiment is 42.7 mm.

The mass of the golf ball 2 is preferably 40 g or more and 50 g or less. From the viewpoint that a large inertia can be obtained, the mass is more preferably 44 g or more, and particularly preferably 45.00 g or more. From the viewpoint that the USGA standard is satisfied, the mass is particularly preferably 45.93 g or less.

The core 4 is formed by cross-linking the rubber composition. Examples of the base rubber of the rubber composition include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer and natural rubber. Two or more kinds of rubber may be used together. From the viewpoint of resilience performance, polybutadiene is preferable, and high cis polybutadiene is particularly preferable.

The rubber composition of the core 4 contains a co-crosslinking agent. Preferred co-crosslinking agents from the viewpoint of resilience performance are zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. It is preferable that the rubber composition contains an organic peroxide together with a co-crosslinking agent. Preferred organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylper). Oxy) hexane and di-t-butyl peroxide can be mentioned.

The rubber composition of the core 4 may contain additives such as fillers, sulfur, vulcanization accelerators, sulfur compounds, anti-aging agents, colorants, plasticizers and dispersants. The rubber composition may include a carboxylic acid or a carboxylic acid salt. The rubber composition may include synthetic resin powder or crosslinked rubber powder.

The diameter of the core 4 is preferably 30.0 mm or more, and particularly preferably 38.0 mm or more. The diameter of the core 4 is preferably 42.0 mm or less, and particularly preferably 41.5 mm or less. The core 4 may have two or more layers. The core 4 may have ribs on its surface. The core 4 may be hollow.

The intermediate layer 6 is made of a resin composition. A preferred substrate polymer for this resin composition is an ionomer resin. Preferred ionomer resins include binary copolymers of α-olefins and α, β-unsaturated carboxylic acids having 3 or more and 8 or less carbon atoms. As other preferable ionomer resins, a ternary copolymer of an α-olefin, an α, β-unsaturated carboxylic acid having 3 or more and 8 or less carbon atoms and an α, β-unsaturated carboxylic acid ester having 2 or more and 22 or less carbon atoms Examples include copolymers. In the binary copolymer and the ternary copolymer, preferable α-olefins are ethylene and propylene, and preferable α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In these binary copolymers and ternary copolymers, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ion for neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion and neodium ion.

Instead of the ionomer resin, the resin composition of the intermediate layer 6 may contain other polymers. Examples of other polymers include polystyrene, polyamide, polyester, polyolefin and polyurethane. The resin composition may contain two or more polymers.

The resin composition of the intermediate layer 6 contains a colorant such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent whitening agent and the like. It may be. For the purpose of adjusting the specific gravity, this resin composition may contain powders of high specific gravity metals such as tungsten and molybdenum.

The thickness of the intermediate layer 6 is preferably 0.2 mm or more, and particularly preferably 0.3 mm or more. The thickness of the intermediate layer 6 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the intermediate layer 6 is preferably 0.90 or more, and particularly preferably 0.95 or more. The specific gravity of the intermediate layer 6 is preferably 1.10 or less, and particularly preferably 1.05 or less. The intermediate layer 6 may have two or more layers.

The cover 8 is molded from a resin composition. A preferred substrate polymer for this resin composition is an ionomer resin. The golf ball 2 having the cover 8 containing the ionomer resin has excellent resilience performance. The ionomer resin described above for the intermediate layer 6 can be used for the cover 8.

Instead of the ionomer resin, the resin composition of the cover 8 may contain other polymers. Examples of other polymers include polystyrene, polyamide, polyester, polyolefin and polyurethane. The resin composition may contain two or more polymers.

The resin composition of the cover 8 may contain an appropriate amount of a colorant, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent whitening agent and the like. When the hue of the golf ball 2 is white, the typical colorant is titanium dioxide.

The thickness of the cover 8 is preferably 0.2 mm or more, more preferably 0.4 mm or more, and particularly preferably 0.6 mm or more. The thickness of the cover 8 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the cover 8 is preferably 0.90 or more, and particularly preferably 0.95 or more. The specific gravity of the cover 8 is preferably 1.10 or less, and particularly preferably 1.05 or less.

FIG. 2 shows a cross section of the golf ball 2 along a plane passing through the center of the dimple 12 and the center of the golf ball 2. The vertical direction in FIG. 2 is the depth direction of the dimple 12. What is shown by the alternate long and short dash line 16 in FIG. 2 is a virtual sphere. The surface of the virtual sphere 16 is the surface of the golf ball 2 when it is assumed that the dimples 12 and the microprojections (detailed later) are absent. The diameter of the virtual ball 16 is the same as the diameter of the golf ball 2. The dimple 12 is recessed from the surface of the virtual sphere 16. The land 14 coincides with the surface of the virtual sphere 16.

In FIG. 2, the arrow Dm indicates the diameter of the dimple 12. The diameter Dm of each dimple 12 is preferably 2.0 mm or more and 6.0 mm or less. In FIG. 2, the double-headed arrow Dp indicates the depth of the dimple 12. This depth Dp is the distance between the deepest part of the dimple 12 and the surface of the virtual sphere 16. The depth Dp is preferably 0.10 mm or more and 0.65 mm or less.

The area s of the dimple 12 is the area of the area surrounded by the contour of the dimple 12 when the center of the golf ball 2 is viewed from infinity. In the case of the circular dimples 12, the area S is calculated by the following formula.
S = (Dm / 2) ² * π

In the present invention, the ratio of the total area S of all dimples 12 to the surface area of the virtual sphere 16 is referred to as the occupancy rate. From the viewpoint that sufficient turbulence can be obtained, the occupancy rate So is preferably 75% or more. The occupancy rate is preferably 95% or less.

From the viewpoint that a sufficient occupancy rate is achieved, the total number N of the dimples 12 is preferably 250 or more. From the viewpoint that each dimple 12 can contribute to turbulence, the total number N is preferably 450 or less.

In the present invention, the "volume of dimples" means the volume of a portion surrounded by the surface of the virtual sphere 16 and the surface of the dimples 12. From the viewpoint that the hop of the golf ball 2 during flight is suppressed, the total volume of the dimples 12 is preferably 450 mm ³ or more. From the viewpoint of suppressing the drop of the golf ball 2 during flight, the total volume is preferably 750 mm ³ or less.

FIG. 3 is an enlarged perspective view showing a part of the surface of the golf ball 2 of FIG. As is clear from FIG. 3, the golf ball 2 is provided with a large number of microprojections 18 on its surface. As is clear from FIG. 2, the microprojections 18 are formed on the surface of the dimples 12 and also on the surface of the lands 14. Each of the microprojections 18 stands outward in the radial direction of the golf ball 2. The microprojections 18 may be formed only on the surface of the dimples 12. The microprojections 18 may be formed only on the surface of the land 14.

FIG. 3 shows three microprojections 18a belonging to the first row I and three microprojections 18b belonging to the second row II. The direction indicated by the arrow A in FIG. 3 is the extending direction of the row. In each row, the microprojections 18 are arranged at equal pitches. In other words, the microprojections 18 are regularly arranged. The microprojections 18 may be arranged irregularly on a part of the surface of the golf ball 2.

The microprojections 18a belonging to the first row I and the microprojections 18b belonging to the second row II may be arranged in a zigzag pattern. In other words, the position of the microprojection 18a belonging to the first row I may deviate from the position of the microprojection 18b belonging to the second row II in the extending direction A.

FIG. 4 is an enlarged cross-sectional view showing a part of the golf ball 2 of FIG. FIG. 4 shows a cover 8 which is a part of the main body 10 and a paint layer 20. FIG. 4 shows the microprojections 18. The cover 8 has a convex portion 22. The microprojection 18 is formed by the convex portion 22 and the paint layer 20. Since the convex portion 22 stands outward in the radial direction of the golf ball 2 (upward in FIG. 4), the microprojection 18 also stands outward in the radial direction of the golf ball 2. In other words, the microprojection 18 has a shape that reflects the surface shape of the main body 10 (cover 8). In FIG. 4, the bottom surface of the microprojection 18 is indicated by reference numeral 24.

FIG. 5 is a cross-sectional view taken along the line VV of FIG. FIG. 5 shows the bottom surface 24 of the microprojection 18. The bottom surface 24 includes a cover 8 and a paint layer 20.

What is indicated by the arrow P in FIG. 3 is the pitch. The pitch P is the distance between the first microprojection 18 and the second microprojection 18 adjacent to the first microprojection 18. The pitch P is the distance between the center of gravity of the bottom surface 24 of the first microprojection 18 and the center of gravity of the bottom surface 24 of the second microprojection 18. The "second microprojection adjacent to the first microprojection" is the microprojection 18 having the shortest distance from the first microprojection 18 among the microprojections 18 existing around the first microprojection 18. Is. This "distance" is the distance between the centers of gravity of the bottom surfaces 24 of the microprojections 18.

One pitch P is determined for each microprojection 18. The average pitch Pav is calculated by summing the pitches P of all the microprojections 18 and dividing this total by the number of microprojections 18. The average pitch Pav is preferably 100 μm or more. Even if mud comes into contact with the golf ball 2 having an average pitch Pav of 100 μm or more, the mud flows through the flow path between the microprojection 18 and the adjacent microprojection 18. Mud does not easily adhere to the golf ball 2. The golf ball 2 has excellent antifouling properties. In the golf ball 2 having an average pitch Pav of 100 μm or more, water also flows through the flow path between the minute protrusion 18 and the minute protrusion 18 adjacent thereto. Therefore, even when the surface of the golf ball 2 becomes dirty, when it is washed with water, this water takes in mud and flows. The golf ball 2 is excellent in cleanability. From the viewpoint of antifouling property and detergency, the average pitch Pav is more preferably 110 μm or more, and particularly preferably 120 μm or more. The average pitch Pav is preferably 2 mm or less from the viewpoint that the flow path is easily formed.

In FIG. 3, the arrow L indicates the distance between the first microprojection 18 and the second microprojection 18 adjacent to the first microprojection 18. The direction of the distance L is the same as the direction of the pitch P.

One distance L is determined for each microprojection 18. The average distance Lav is calculated by summing the distances L of all the microprojections 18 and dividing this total by the number of microprojections 18. From the viewpoint that the flow path is easily formed, the average distance Lav is preferably 40 μm or more, more preferably 60 μm or more, and particularly preferably 75 μm or more. The average distance Lav is preferably 400 μm or less.

In FIG. 5, along with the bottom surface 24c of the first microprojection 18c, the bottom surface 24d of the second microprojection 18d is also shown by a chain double-dashed line. The second microprojection 18d is adjacent to the first microprojection 18c. In FIG. 5, the alternate long and short dash line 26 is a straight line passing through the center of gravity Oc of the bottom surface 24c of the first microprojection 18c and the center of gravity Od of the bottom surface 24d of the second microprojection 18d. In FIG. 5, the arrow T indicates the width of the first microprojection 18c. The width T is measured along a straight line 26. The width T is the distance of the portion of the straight line 26 included in the contour of the bottom surface 24c.

In FIG. 6, along with the bottom surface 24c of the first microprojection 18c, the bottom surface 24e of the second microprojection 18e is also shown by a chain double-dashed line. The second microprojection 18e is adjacent to the first microprojection 18c. In FIG. 6, the alternate long and short dash line 28 is a straight line passing through the center of gravity Oc of the bottom surface 24c of the first microprojection 18c and the center of gravity Oe of the bottom surface 24e of the second microprojection 18e. In FIG. 6, the arrow T indicates the width of the first microprojection 18c. The width T is measured along a straight line 28. The width T is the distance of the portion of the straight line 28 included in the contour of the bottom surface 24c. The width T shown in FIG. 6 is larger than the width T shown in FIG.

The distance between the first microprojection 18c and the second microprojection 18d shown in FIG. 5 is equal to the distance between the first microprojection 18c and the second microprojection 18e shown in FIG. The first microprojection 18c is adjacent to the two second microprojections 18d, 18e. Therefore, the first microprojection 18c may have a plurality of widths T. In this case, the largest width T is adopted as the width of the first microprojection 18c.

One width T is determined for each microprojection 18. The average width Tav is calculated by summing the widths T of all the microprojections 18 and dividing this total by the number of microprojections 18. From the viewpoint of antifouling property, the average width Tav is preferably 40 μm or more, more preferably 50 μm or more, and particularly preferably 75 μm or more. From the viewpoint that the flow path is easily formed, the average width Tav is preferably 400 μm or less.

The golf ball 2 satisfies the following mathematical formula.
Lav> 0.5 ・ Tav
In the golf ball 2, a flow path is likely to be formed between the microprojection 18 and the microprojection 18 adjacent thereto. When the golf ball 2 is washed with water, the water takes in mud and flows. Therefore, the golf ball 2 is excellent in antifouling property and cleanability. From the viewpoint of antifouling property and cleanability, it is preferable that the golf ball 2 satisfies the following formula.
Lav ≧ Tav
It is preferable that the golf ball 2 satisfies the following formula.
Lav <1.5 ・ Tav

In FIG. 4, the arrow H indicates the height of the microprojection 18. The height H is measured along the radial direction of the golf ball 2. The average height Hav is calculated by summing the heights H of all the microprojections 18 and dividing this total by the number of microprojections 18. The average height Hav is preferably 0.5 μm or more, more preferably 1.0 μm or more, and 2.0 μm or more, from the viewpoint that a flow path is easily formed between the microprojection 18 and the microprojection 18 adjacent thereto. Is particularly preferable. From the viewpoint of the flight performance of the golf ball 2, the average height Hav is preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less.

From the viewpoint of antifouling property and detergency, the average area is preferably 100 [mu] m ² or more bottom 24, more preferably 225 .mu.m ² or more, 400 [mu] m ² or more is particularly preferable. From the viewpoint of antifouling property, the average area is preferably 3600Myuemu ² or less, more preferably 2500 [mu] m ² or less, 1600 .mu.m ² or less is particularly preferred.

From the viewpoint of antifouling property and cleanability, the ratio of the total area of the bottom surface 24 of all the microprojections 18 to the surface area of the virtual sphere 16 is preferably 5% or more, more preferably 15% or more, and particularly 20% or more. preferable. From the viewpoint of antifouling property, this ratio is preferably 80% or less, more preferably 60% or less, and particularly preferably 50% or less.

From the viewpoint of antifouling property and detergency, the total number of microprojections 18 is preferably 500 or more, more preferably 1000 or more, and particularly preferably 2000 or more. From the viewpoint of antifouling property, the total number is preferably 500,000 or less, more preferably 300,000 or less, and particularly preferably 100,000 or less.

As described above, the microprojection 18 includes the convex portion 22 of the main body 10 and the paint layer 20 (see FIG. 4). Therefore, even if the paint layer 20 is peeled from the main body 10, the shape of the microprojections 18 is generally maintained and the flow path is maintained. No special paint is required to form the microprojections 18. The golf ball 2 can be easily manufactured.

In this golf ball 2, contamination is prevented by the physical action of the microprojections 18. Therefore, it is not necessary to employ the cover 8 and the paint layer 20 having special chemical properties for the purpose of antifouling.

The convex portion 22 of the main body 10 is formed at the same time as the main body 10 is formed. A molding die is used for this molding. The cavity surface of this molding has a large number of minute recesses. Each concave portion has a shape in which the shape of the convex portion 22 is substantially inverted. This mold can be obtained from a master mold. Etching is an example of a method for producing this master mold. A large number of micromasks are used during etching. By masking, a convex portion is formed on the master mold. The convex portion of the master mold forms a concave portion in the molding mold. The masking position corresponds to the position of the convex portion of the master mold, corresponds to the position of the concave portion of the molding mold, and corresponds to the position of the minute protrusion 18 of the golf ball 2. Master molds can be made by various methods other than etching. Laser irradiation processing is exemplified as a method other than etching.

As described above, the microprojections 18 are formed on the surface of the dimples 12 and also on the surface of the lands 14 (see FIG. 2). The microprojections 18 prevent the dimples 12 from being contaminated and also prevent the lands 14 from being contaminated.

The shape of the microprojection 18 shown in FIG. 2-6 is approximately a quadrangular prism. The golf ball 2 may have microprojections of other shapes. Examples of other shapes include prisms other than prisms, cylinders, truncated cones, truncated cones, pyramids and cones. The shape of the microprojections may be part of a sphere. The microprojections may have a shape in which a plurality of solids are combined.

Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed in a limited way based on the description of the examples.

[Example 1]
100 parts by mass of high cis polybutadiene (JSR brand name "BR-730"), 25.5 parts by mass of zinc acrylate, 12 parts by mass of zinc oxide, appropriate amount of barium sulfate, 0.5 parts by mass of diphenyldisulfide , 0.9 parts by mass of dicumyl peroxide, 0.1 parts by mass of 2-naphthalene thiol and 2 parts by mass of benzoic acid were kneaded to obtain a rubber composition. This rubber composition was put into a mold consisting of an upper mold and a lower mold both having a hemispherical cavity, and heated at 160 ° C. for 20 minutes to obtain a core having a diameter of 38.7 mm. The amount of barium sulfate was adjusted so that a core having a predetermined mass was obtained.

26 parts by mass of ionomer resin (trade name "Himilan AM7337" by Mitsui DuPont Polychemical), 26 parts by mass of other ionomer resin (trade name "Himilan AM7329" by Mitsui DuPont Polychemical), 48 parts by mass styrene block Biaxial containing thermoplastic elastomer (trade name "Labaron T3221C" of Mitsubishi Chemical Co., Ltd.), 4 parts by mass of titanium dioxide and 0.2 parts by mass of light stabilizer (trade name "JF-90" of Johoku Chemical Industry Co., Ltd.) A resin composition was obtained by kneading with a kneading extruder. This resin composition was coated around the core by an injection molding method to form an intermediate layer. The thickness of this intermediate layer was 1.0 mm.

55 parts by mass of ionomer resin (trade name "Himilan AM7329" by Mitsui DuPont Polychemical), 45 parts by mass of other ionomer resin (trade name "Himilan 1555" by Mitsui DuPont Polychemical), 4 parts by mass titanium dioxide And 0.2 parts by mass of a light stabilizer (trade name "JF-90" of Johoku Chemical Industry Co., Ltd.) was kneaded with a twin-screw kneading extruder to obtain a resin composition. A sphere composed of a core and an intermediate layer was put into a final mold consisting of an upper mold and a lower mold, each having a hemispherical cavity and having a large number of pimples and microrecesses on the cavity surface. The resin composition was coated around the intermediate layer by an injection molding method to form a cover. The thickness of this cover was 1.0 mm. The cover was formed with dimples having an inverted shape of the pimples. The cover was further formed with minute protrusions having an inverted shape of the minute recesses.

A clear paint based on a two-component curable polyurethane was applied around the cover to obtain a golf ball of Example 1 having a diameter of about 42.7 mm and a mass of about 45.6 g. This golf ball has a large number of microprojections on its surface. The specifications of these microprojections are shown in Table 1 below.

[Examples 2-4 and 8 and Comparative Example 1]
Examples 2-4 and Examples 2-4 and the same as in Example 1 except that the final mold was changed to form microprojections having an average pitch Pa, an average distance La, and an average width Ta shown in Table 1-2 below. 8 and the golf balls of Comparative Example 1 were obtained.

[Example 5-7]
The golf ball of Example 5-7 was obtained in the same manner as in Example 1 except that the final mold was changed to form microprojections having an average height Ha shown in Table 1-2 below.

[Comparative Example 2]
A golf ball of Comparative Example 2 was obtained in the same manner as in Example 1 except that the final mold was changed and no microprojections were formed.

[Anti-fouling property]
Soil and water were mixed to obtain mud. Along with this mud, the golf balls according to each Example and each Comparative Example were put into a bucket and the mud was stirred. The degree of dirt on the golf ball after that was rated according to the following criteria.
A: Very low dirt B: Low dirt C: High dirt D: Very high dirt The results are shown in Tables 1 and 2 below.

[Cleanability]
The golf ball used for the evaluation of the antifouling property was put into a bucket together with water, and the water was stirred. The degree of dirt on the golf ball after that was rated according to the following criteria.
A: Very low dirt B: Low dirt C: High dirt D: Very high dirt The results are shown in Tables 1 and 2 below.

As shown in Tables 1 and 2, the golf balls of each embodiment are excellent in antifouling property and cleanability. From this evaluation result, the superiority of the present invention is clear.

The above-mentioned microprojections are applied not only to three-piece golf balls, but also to golf balls having various structures such as one-piece golf balls, two-piece golf balls, four-piece golf balls, five-piece golf balls, six-piece golf balls, and thread-wound golf balls. Can be done.

2 ... Golf ball 4 ... Core 6 ... Intermediate layer 8 ... Cover 10 ... Main body 12 ... Dimple 14 ... Land 16 ... Virtual ball 18 ... Micro protrusion 20・ ・ ・ Paint layer 22 ・ ・ ・ Convex part 24 ・ ・ ・ Bottom

Claims (3)

A golf ball with multiple dimples and lands
It further comprises a large number of microprojections formed on the surface of the dimples and / or lands.
The distance between the centers of gravity of the bottom surfaces of the second microprojection, which has the smallest distance between the first microprojection and the first microprojection among the microprojections existing around it, was defined as the pitch of the first microprojection. when, Ri 2mm der than the mean value Pav is 100μm or more, which is calculated by the sum pitch P of all the first microprotrusions are summed are divided by the number of microprojections,
The average height Hav calculated by summing the heights H of all the microprojections measured along the radial direction of the golf ball and dividing this total by the number of microprojections is 5 μm or more and 30 μm or less. ,
A golf ball that satisfies the following formula .
Lav> 0.5 ・ Tav
(In the above formula, Lav represents an average value calculated by summing the distance L between the first microprojection and the second microprojection and dividing this by the number of microprojections, and Tav is The maximum value in the width T of the first microprojection measured along a straight line passing through the center of gravity of the bottom surface of the first microprojection and the center of gravity of the bottom surface of the second microprojection is totaled. It represents an average value calculated by dividing by the number of microprojections. The average value Lav is 40 μm or more and 400 μm or less, and the average value Tav is 40 μm or more and 400 μm or less.) The golf ball according to claim 1 , which has a plurality of rows, and a plurality of microprojections are arranged at equal pitches in each row. It has a main body and a paint layer located on the outside of this main body.
The golf ball according to claim 1 or 2 , wherein the microprojections have a shape that reflects the surface shape of the main body.

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