JP2018192282A - Golf ball and method of manufacturing the same - Google Patents

Abstract

To provide a golf ball that improves flight performance.SOLUTION: A golf ball according to the present invention comprises a spherical core, at least one cover member for covering the core, and a coating layer for coating the cover member constituting an outermost layer. The cover member constituting the outermost layer is formed with a plurality of dimples. Roughness is formed on a surface of the coating layer so that a relationship between a drag coefficient CD1 and a lift coefficient CL1 when the ball is hit on condition of Reynolds number of 1.771×10and a spin amount of 2280 rpm can satisfy the inequality: CD1×CL1<0.0370.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a golf ball and a manufacturing method thereof.

  The golf ball has a large number of dimples on its surface. The dimples disturb the air flow around the golf ball during flight and cause turbulent separation. This phenomenon is referred to as “turbulent flow”. By this turbulent flow, the separation point of air from the golf ball shifts backward, and drag is reduced. Further, the turbulent flow promotes the deviation between the upper peeling point and the lower peeling point of the golf ball due to backspin, and the lift acting on the golf ball is enhanced. Thus, excellent dimples better disturb the air flow and produce a large flight distance.

Japanese Patent Laid-Open No. 10-234885

  By the way, for example, when a golfer hits with a middle iron, a lot of spin is generated, and as a result, the ball muscles blow up and the flight distance may not be extended. Such problems are not limited to middle irons, but conventionally, efforts have been made to improve dimple specifications for the purpose of suppressing this rise in dimple design. However, this problem has not been solved yet, and an improvement in aerodynamic performance that is not restricted by dimple design is desired. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a golf ball that improves flight performance.

The golf ball according to the present invention includes a spherical core, at least one cover member that covers the core, and a coating layer that covers the cover member that forms the outermost layer, and the cover member that forms the outermost layer. Are formed with a plurality of dimples, and the relationship between the drag coefficient CD1 and the lift coefficient CL1 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2280 rpm satisfies CD1 × CL1 <0.0370. Thus, roughness is formed on the surface of the coating layer.

In the golf ball, the coating layer is formed so that the relationship between the drag coefficient CD2 and the lift coefficient CL2 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2940 rpm satisfies CD2 × CL2 <0.0410. Roughness can be formed on the surface.

  In the golf ball, the arithmetic average roughness Ra of the surface of the coating layer can be 0.5 μm or more, and the maximum height Rz can be 4.0 μm or more.

A golf ball manufacturing method according to the present invention includes a step of forming a spherical core, a step of covering the core with at least one cover member, and forming a plurality of dimples on the cover member constituting the outermost layer, The relationship between the step of covering the cover member constituting the outer layer with a coating layer and the drag coefficient CD1 and the lift coefficient CL1 when struck at a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2280 rpm is CD1 × CL1 <0. Forming a roughness on the surface of the coating layer so as to satisfy 0370.

In the golf ball manufacturing method, in the step of forming the roughness, the relationship between the drag coefficient CD2 and the lift coefficient CL2 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2940 rpm is CD2 × CL2 <0. The surface of the coating layer can be roughened so as to satisfy 0.041.

  In the golf ball manufacturing method, the arithmetic average roughness Ra of the roughness formed on the surface of the coating layer can be 0.5 μm or more, and the maximum height Rz can be 4.0 μm or more.

  According to the golf ball and the manufacturing method thereof according to the present invention, the flight performance can be improved.

1 is a partially cutaway sectional view showing an embodiment of a golf ball of the present invention. It is a partially expanded sectional view of FIG. It is the schematic explaining the force which acts on a golf ball.

<1. Golf ball>
Hereinafter, an embodiment of a golf ball according to the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway sectional view of a golf ball according to the present embodiment.

  As shown in FIG. 1, the golf ball includes a spherical core 1, an intermediate layer 2 covering the core 1, a cover 3 covering the intermediate layer 2, and a coating layer 4 coated on the surface of the cover 3. And.

  The diameter of the golf ball is preferably 40 to 45 mm, and more preferably 42.67 mm or more from the viewpoint of satisfying the standards of the American Golf Association (USGA). From the viewpoint of suppressing air resistance, the diameter is preferably 44 mm or less, and more preferably 42.80 mm or less. The golf ball preferably has a mass of 40 g or more and 50 g or less. In particular, from the viewpoint of obtaining large inertia, the mass is preferably 44 g or more, and more preferably 45.00 g or more. Further, from the viewpoint of satisfying the USGA standard, it is preferably 45.93 g or less.

<1-1. Core>
Next, each member constituting the golf ball will be described. The core 1 is formed by crosslinking a 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 rubbers may be used in combination. Further, from the viewpoint of resilience performance, polybutadiene is preferable, and high cis polybutadiene is particularly preferable.

  The rubber composition of the core 1 contains a co-crosslinking agent. From the viewpoint of resilience performance, preferred co-crosslinking agents 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-butylperoxy). ) Hexane and di-t-butyl peroxide.

  The rubber composition of the core 1 may contain additives such as a filler, sulfur, a vulcanization accelerator, a sulfur compound, an antioxidant, a colorant, a plasticizer, a dispersant, a carboxylic acid, and a carboxylate. Further, the rubber composition may include a synthetic resin powder or a crosslinked rubber powder.

  The diameter of the core 1 is preferably 30.0 mm or more, and particularly preferably 38.0 mm or more. On the other hand, the diameter of the core 1 is preferably 42.0 mm or less, and particularly preferably 41.5 mm or less. The core 1 may have two or more layers. The shape of the core 1 is not particularly limited as long as it is spherical as a whole, but may have ribs on the surface thereof. Moreover, the core 1 may be hollow.

<1-2. Intermediate layer>
Next, the intermediate layer 2 will be described. The intermediate layer 2 is made of a resin composition. A preferred base polymer of this resin composition is an ionomer resin. A preferable ionomer resin includes a binary copolymer of α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. As another preferable ionomer resin, a ternary copolymer of α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester having 2 to 22 carbon atoms is used. A polymer is mentioned. In this binary copolymer and ternary copolymer, preferred α-olefins are ethylene and propylene, and preferred α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In this binary copolymer and ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ions for neutralization include sodium ions, potassium ions, lithium ions, zinc ions, calcium ions, magnesium ions, aluminum ions, and neodymium ions.

  Instead of the ionomer resin, the resin composition of the mid layer 2 may contain another polymer. Examples of other polymers include polystyrene, polyamide, polyester, polyolefin, and polyurethane. The resin composition may contain two or more kinds of polymers.

  The resin composition of the intermediate layer 2 includes 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. But you can. For the purpose of adjusting the specific gravity, the resin composition may contain a powder of a high specific gravity metal such as tungsten or molybdenum.

  The thickness of the intermediate layer 2 is preferably 0.2 mm or more, particularly preferably 0.3 mm or more. On the other hand, the thickness of the intermediate layer 2 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the intermediate layer 2 is preferably 0.90 or more, particularly preferably 0.95 or more. The specific gravity of the intermediate layer 2 is preferably 1.10 or less, particularly preferably 1.05 or less. The intermediate layer 2 may have two or more layers. For example, a reinforcing layer can be disposed outside the intermediate layer 2.

<1-3. Cover>
The cover 3 is made of a resin composition. A preferred base polymer of this resin composition is polyurethane. The resin composition may contain a thermoplastic polyurethane or a thermosetting polyurethane. From the viewpoint of productivity, thermoplastic polyurethane is preferred. The thermoplastic polyurethane includes a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment.

  Examples of the curing agent for the polyurethane component include alicyclic diisocyanate, aromatic diisocyanate and aliphatic diisocyanate. In particular, alicyclic diisocyanates are preferred. Since the alicyclic diisocyanate does not have a double bond in the main chain, yellowing of the cover 8 is suppressed. As alicyclic diisocyanates, 4,4, -dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), isophorone diisocyanate (IPDI) and trans-1,4-cyclohexane diisocyanate (CHDI) Is exemplified. From the viewpoint of versatility and workability, H12MDI is preferable.

  Instead of polyurethane, the resin composition of the cover 3 may contain another polymer. Examples of other polymers include ionomer resin, polystyrene, polyamide, polyester, and polyolefin. The resin composition may contain two or more kinds of polymers.

  Even if the resin composition of the cover 3 includes 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. Good.

  The thickness of the cover 3 is preferably 0.2 mm or more, and more preferably 0.3 mm or more. The thickness of the cover 3 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the cover 3 is preferably 0.90 or more, and particularly preferably 0.95 or more. The specific gravity of the cover 3 is preferably 1.10 or less, and particularly preferably 1.05 or less. The cover 3 may have two or more layers.

A dimple 5 is formed on the surface of the cover 3. In FIG. 2, a tangent line common to both ends of the dimple 5 is indicated by a virtual line T. The volume of the portion surrounded by the virtual line T and the surface of the dimple 5 is the volume of the dimple 5. The total volume of the dimples 5 is preferably 270 mm ³ or more and 370 mm ³ or less. If the total volume is less than the above range, a hopping trajectory may occur. In this respect, the total volume is more preferably 290 mm ³ or more. If the total volume exceeds the above range, the trajectory may drop. In this respect, the total volume is more preferably equal to or less than 350 mm ³ .

  The ratio of the total area of the dimples 5 to the surface area of the phantom sphere is referred to as the surface area occupation ratio. The surface area occupation ratio is preferably 70% or more and 90% or less. If the surface area occupation ratio is less than the above range, the lift of the golf ball in flight may be insufficient. In this respect, the surface area occupation ratio is more preferably 72% or more, and particularly preferably 75% or more. On the other hand, when the surface area occupancy exceeds the above range, a hopping trajectory may occur. In this respect, the surface area occupation ratio is preferably 88% or less, and more preferably 86% or less. The area of the dimple 5 is the area of the region surrounded by the edge line (that is, the area of the planar shape) when the center of the golf ball is viewed from infinity.

  The depth of each dimple 5 is preferably 0.1 mm or greater and 0.6 mm or less. If the depth is less than the above range, a hopping trajectory may occur. In this respect, the depth is more preferably equal to or greater than 0.12 mm, and particularly preferably equal to or greater than 0.14 mm. On the other hand, if the depth exceeds the above range, the trajectory may drop. In this respect, the depth is more preferably equal to or less than 0.55 mm, and particularly preferably equal to or less than 0.50 mm. The ratio of the number of dimples 5 whose depth is included in the above range to the total number of dimples 5 is preferably 50% or more, more preferably 65% or more, and particularly preferably 80% or more. The depth is a distance from the imaginary line T to the deepest part of the dimple 5.

  The total number of dimples 5 is preferably 200 or more and 500 or less. When the total number is less than the above range, it is difficult to obtain the dimple effect. In this respect, the total number is more preferably 230 or more, and particularly preferably 260 or more. On the other hand, when the total number exceeds the above range, it is difficult to obtain the dimple effect. In this respect, the total number is more preferably 470 or less, and particularly preferably 440 or less.

  The dimples 5 to be formed may be a single type or a plurality of types. Instead of the circular dimple 5 or together with the circular dimple 5, a non-circular dimple (a dimple whose planar shape is not a circle) may be formed.

<1-4. Paint layer>
Next, the coating layer 4 will be described. The coating layer 4 is configured by coating the surface of the cover 3 with a paint. As such a paint, for example, a clear paint based on a two-component curable polyurethane can be used, but is not particularly limited as long as it is a paint.

  The thickness of the coating layer 4 is preferably 5.0 μm or more, more preferably 5.5 μm or more, and particularly preferably 6.0 μm or more. This is because if the thickness of the coating layer 4 is smaller than 5.0 μm, peeling from the cover 3 may occur in the process of forming roughness described later. On the other hand, the upper limit of the thickness of the coating layer 4 is not particularly limited, but if the thickness of the coating layer 4 is increased by increasing the amount of coating applied, the thickness of the coating layer 4 on the entire ball may not be uniform. High nature. From this viewpoint, the thickness of the coating layer 4 is preferably 30 μm or less.

  Further, roughness is formed on the surface of the coating layer 4. That is, as will be described later, after the coating layer 4 having no roughness is formed on the cover 3, roughness is formed on the surface of the coating layer 4. This roughness is for improving the aerodynamic effect of the golf ball, and is formed from the following viewpoints.

Here, a force as shown in FIG. 3 acts on the hit golf ball. That is, gravity, drag by air in the direction opposite to the flight direction, and lift by spin of the ball act. Therefore, the force vector F acting on the ball is expressed by the following equation.
F = F _L + F _D + F _G (1)
F _L : Lift vector F _D : Drag vector F _G : Gravity vector

The lift vector and the drag vector are expressed by the following equations.
F _L + = 0.5 * CD * ρ * A * V ² (2)
F _D + = 0.5 * CD * ρ * A * V ² (3)
CD: Drag coefficient CL: Lift coefficient ρ: Air density A: Golf ball projected area V: Golf ball speed Note that the drag coefficient CD and the lift coefficient CL are in accordance with ITR (Indoor Test Range) defined in USGA rules. Measured.

Therefore, in order to increase the flight distance, it is necessary to reduce both CD and CL. Therefore, in the golf ball according to the present embodiment, as the condition 1, the relationship between the drag coefficient CD1 and the lift coefficient CL1 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin amount of 2280 rpm is CD1 × CL1 <0.0370. Roughness is formed on the surface of the coating layer 4 so as to satisfy (Expression (4)).

Further, in addition to forming the roughness so as to satisfy the relationship of the aerodynamic characteristics in the condition 1, it is also possible to form the roughness so as to satisfy the relationship of the aerodynamic characteristics in the following condition 2. That is, as condition 2, the relationship between the drag coefficient CD2 and the lift coefficient CL2 when hitting with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2940 rpm satisfies CD2 × CL2 <0.0410 (formula (5)). As described above, roughness can be formed on the coating layer 4.

  Conditions 1 and 2 are similar to the initial conditions for launching by a hard hitter among average golfers. More specifically, Condition 1 assumes a spin amount close to the amount of spin generated by an average golfer, and Condition 2 assumes a spin amount greater than the spin amount generated by an average golfer. . Then, the inventors of the present invention have found that satisfying the relationship between the drag coefficients CD1 and CD2 and the lift coefficients CL1 and CL2 in the above condition 1 or 2 leads to an increase in flight distance. . For example, if condition 1 is satisfied, an increase in flight distance can be expected for an average golfer. Further, when the condition 2 is satisfied, the above-described effect can be expected even in a case where the spin rate is too high and the sphere rises too much or the average golfer takes too much spin in a miss shot. A golf ball that satisfies both Condition 1 and Condition 2 has the effect of increasing the flight distance in most of the average golfer's spin conditions, particularly in a region with a lot of spin.

  In order to obtain the aerodynamic characteristics as described above, the roughness can be formed by various methods. For example, the maximum height Rz and the arithmetic average roughness Ra of the surface of the coating layer 4 are set as follows. By setting, the aerodynamic characteristics described above can be obtained.

  That is, the arithmetic average roughness Ra of the coating layer 4 is preferably 0.5 μm or more, more preferably 0.6 μm or more, and particularly preferably 0.7 μm or more. This is because if the arithmetic average roughness Ra is smaller than 0.5 μm, the aerodynamic effect due to the roughness cannot be obtained sufficiently. On the other hand, the upper limit of the arithmetic average roughness Ra is not particularly limited. However, if the roughness increases, adhesion failure or peeling of the coating layer 4 to the cover 3 may occur.

  On the other hand, the maximum height Rz is preferably 4.0 μm or more, more preferably 4.5 μm or more, and particularly preferably 5.0 μm or more. This is because if the maximum height Rz is smaller than 4.0 μm, the aerodynamic effect due to roughness cannot be sufficiently obtained. On the other hand, the upper limit of the maximum height Rz is not particularly limited. However, if the roughness increases, adhesion failure or peeling of the coating layer 4 to the cover 3 may occur. In addition, these maximum height Rz and arithmetic mean roughness Ra are measured based on prescription | regulation of JISB0601 (2001).

<2. Golf Ball Manufacturing Method>
This golf ball is manufactured as follows. As a method for manufacturing such a golf ball, a known method is appropriately used. First, the core 1 is formed, and the intermediate layer 2 and the cover 3 are formed around the core 1 in this order. At the same time as the cover 3 is formed, the dimples 5 are formed. That is, a large number of convex portions for forming dimples are formed in the cavity of the mold for forming the cover. Following this, paint is applied to the surface of the cover 3. The paint layer 4 is obtained by drying the paint.

  The coating method in the case of using a curable paint is not particularly limited, and a known method can be adopted, and examples thereof include spray coating and electrostatic coating.

  In the case of spray coating using an air gun, the polyol component and the polyisocyanate component are supplied by respective pumps, continuously mixed with a line mixer placed immediately before the air gun, and the resulting mixture is spray coated. Alternatively, the polyol and the polyisocyanate may be separately spray-coated using an air spray system equipped with a mixing ratio control mechanism. The coating may be performed by spraying once or by multiple coatings.

  The curable paint applied to the golf ball main body can form a coating film by drying at a temperature of 30 ° C. to 70 ° C. for 1 hour to 24 hours, for example.

<3. Method for forming roughness of coating layer>
Then, the formation method of the roughness of the coating layer 4 is demonstrated. There are various methods for forming the coating layer 4. For example, there are the following two methods.
<3-1. Surface treatment by spraying fine particles>
In this method, the roughness is formed by spraying fine particles on the surface of the coating layer 4. The fine particles can be sprayed over the entire surface with an air gun or the like, for example, while rotating the ball. The spraying pressure at that time is preferably 1 to 10 bar. This is because if it is less than 1 bar, it is difficult to obtain a desired roughness, while if it is greater than 10 bar, not only the coating layer 4 but also the cover 3 may be damaged.

Various fine particles can be used as the fine particles used in this method. For example, natural ores, synthetic resins, ceramic particles, and the like can be used. Examples of natural ores include, for example, SiC, SiO ₂ , AL ₂ O ₃ , MgO, Na ₂ O or a mixture thereof, and synthetic resins include, for example, melamine-based resins as the main component, thermoplastic resins and thermosetting. Resin or a mixture thereof can be used. Examples of the ceramic particles include metal oxides such as zirconia. However, in order to obtain a desired roughness, it is preferable to use fine particles having an average particle size of 50 μm or more. Although the upper limit of the average particle diameter of the fine particles is not particularly limited, it may be difficult to spray as the particle diameter increases, so that it is preferably 500 μm or less.

  In addition, when forming roughness by this method, when the thickness of the coating layer 4 is too small, the coating layer 4 may peel off at the time of spraying of fine particles. From this viewpoint, the thickness of the coating layer 4 is as described above.

<3-2. Pressure treatment>
In this method, after the coating layer 4 is formed, a desired roughness is obtained by applying a pressure treatment using a mold having a roughness formed on the inner wall surface of the cavity. Therefore, a desired roughness is formed on the inner wall surface of the cavity. Although the metal mold | die used here is not specifically limited as long as the roughness is formed, For example, the same thing as what was used for shaping | molding of a dimple can be used. The roughness can be formed on the inner wall surface of the cavity by spraying fine particles as described above.

  In addition, when forming roughness by this method, when the thickness of the coating layer 4 is too small, it is difficult to obtain a desired roughness. From this viewpoint, the thickness of the coating layer 4 is as described above.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this Embodiment, A various change is possible unless it deviates from the meaning. For example, as described above, the number of layers of the core 1, the intermediate layer 2, and the cover 3 is not particularly limited as long as at least the surface of the outermost layer member is covered with the coating layer. In the above embodiment, the core 1, the intermediate layer 2, and the cover 3 are configured. The intermediate layer and the cover correspond to the cover member of the present invention. Moreover, it can also be set as the two-piece structure of a core and a cover.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

  Here, a total of eight types of golf balls of Examples 1 to 6 and Comparative Examples 1 and 2 were examined. These golf balls have the same basic specifications but different surface roughness, CD, and CL. Therefore, the common specification will be described first.

(Common specifications)
100 parts by weight of high-cis polybutadiene (trade name “BR-730” from JSR), 35 parts by weight of zinc acrylate, 5 parts by weight of zinc oxide, 5 parts by weight of barium sulfate, 0.5 parts by weight of diphenyl Disulfide, 0.9 part by mass of dicumyl peroxide and 2.0 parts by mass of zinc octoate were kneaded to obtain a rubber composition. This rubber composition was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity and heated at 170 ° C. for 18 minutes to obtain a core having a diameter of 39.7 m.

  50 parts by weight of ionomer resin (DuPont's trade name “Surlin 8945”), 50 parts by weight of other ionomer resin (Mitsui DuPont Polychemicals trade name “Himiran AM7329”), 4 parts by weight of titanium dioxide and 0 parts by weight .04 parts by mass of ultramarine blue was kneaded with a twin-screw kneading extruder to obtain a resin composition. 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.

  A coating composition (trade name “Porin 750LE”, manufactured by Shinto Paint Co., Ltd.) using a two-component curable epoxy resin as a base polymer was prepared. The main component liquid of this coating composition was 30 parts by mass of a bisphenol A type solid epoxy resin. The curing agent liquid of this coating composition is composed of 40 parts by mass of modified polyamidoamine, 55 parts by mass of solvent, and 5 parts by mass of titanium oxide. The mass ratio with respect to the curing agent liquid was 1/1, and this coating composition was applied to the surface of the intermediate layer with a spray gun and held at 23 ° C. for 6 hours to obtain a reinforcing layer. The thickness of the reinforcing layer was 10 μm.

  100 parts by mass of a thermoplastic polyurethane elastomer (BASF Japan trade name “Elastolan XNY85A”) and 4 parts by mass of titanium dioxide were kneaded with a twin screw extruder to obtain a resin composition. A half shell was obtained from this resin composition by compression molding. A sphere composed of a core, an intermediate layer and a reinforcing layer was covered with two half shells. The half shell and the sphere were both put into a final mold including an upper mold and a lower mold having a hemispherical cavity and a large number of pimples on the cavity surface, and a cover was obtained by a compression molding method. The cover thickness was 0.5 mm. A dimple having a shape obtained by inverting the shape of the pimple was formed on the cover. A clear paint based on a two-component curable polyurethane was applied around the cover to form a coating layer.

  Specifically, the golf ball main body was placed on the rotating body, the rotating body was rotated at 300 rpm, and the air gun was sprayed away from the golf ball main body by a distance of 7 cm and moved up and down. The interval of each overcoating was 1.0 second. The air gun spraying conditions were as follows: spraying air pressure: 0.15 MPa, pressure tank air pressure: 0.10 MPa, one application time: 1 second, ambient temperature: 20 ° C. to 27 ° C., ambient humidity: 65% or less Painted.

  The thickness of the coating layer was all 18 μm, and the clear paint was applied twice. As a result, a golf ball having a diameter of about 42.7 mm and a mass of about 45.6 g was obtained. The amount of compressive deformation measured by a YAMADA compression tester when the load was 98N-1274N was about 2.45 mm. The specifications of this golf ball dimple are shown in Table 1 below.

(Example)
With respect to the golf balls obtained as described above, Examples 1 to 6 formed roughness on the surface of the coating layer by the following method. That is, after the coating layer was formed, fine particles were sprayed with an air gun having a nozzle diameter of 8 mm. At this time, 20 balls were put into a predetermined treatment facility, and fine particles were sprayed at a predetermined pressure for about 1 minute while rotating the facility. The pressure and fine particles used are as shown in Table 2.

(Comparative example)
In Comparative Example 1, the surface is not subjected to surface treatment after the coating layer is formed. In Comparative Example 2, the roughness was formed by spraying fine particles after the formation of the coating layer, as in the above-described Examples. The pressure and fine particles used are as shown in Table 2.

The maximum height Rz, arithmetic average roughness Ra, the above-described CD1, CD2, CL1, CL2, etc. in the examples and comparative examples formed as described above are as shown in Table 2 below.
The maximum height Rz and the arithmetic average roughness Ra were measured using a surface roughness measuring machine, Surfcom 130A manufactured by Tokyo Seimitsu Co., Ltd. Then, six balls were prepared for each example and comparative example, the roughness was measured at six points in an arbitrary dimple of each ball, and the average values were defined as Rz and Ra.

(Evaluation test)
A flight distance test was performed on the example and the comparative example formed as described above.

(Flight distance test)
A metal head driver (Dunlop Sports brand name “SRIXON Z525” (W # 1), carbon shaft hardness: S, loft angle: 9.5 °) was mounted on a swing machine manufactured by Golf Laboratory. The head speed was 47 m / s, and the ball of Comparative Example 1 was adjusted so that the ball speed was 67 m / s, the launch angle was 12.5 degrees, and the spin rate was 2600 rpm. Subsequently, 20 balls of each of the examples and comparative examples were hit, the distance (total) until the hitting ball stopped was measured, and the average value was examined. In addition, the wind direction at the time of the test was almost no wind. The results are shown in Table 3.

(Evaluation)
As shown in Tables 2 and 3, in the flight distance test, the trajectory of the example is generally lower than that of the comparative example. That is, since the roughness of the coating film of an Example is set so that Formula (4) mentioned above may be satisfy | filled, it is thought that lift and drag are reduced. As a result, the flying distance is longer than that of the comparative example. Further, in Examples 3 to 6 that also satisfy Formula (5), the trajectory height is suppressed lower than Examples 1 and 2 that only satisfy Formula (4), and the flight distance is further increased.

Claims (4)

A golf ball,
A spherical core,
At least one cover member covering the core;
A coating layer covering the cover member constituting the outermost layer;
With
The golf ball has a diameter of 40 mm or more and 45 mm or less,
The thickness of the coating layer is 5.0 μm or more,
The cover member constituting the outermost layer is formed with a plurality of dimples,
The total volume of the plurality of dimples is 270 mm ³ or more and 370 mm ³ or less,
The surface area occupation ratio by the plurality of dimples is 70% or more and 90% or less,
The depth of each of the plurality of dimples is 0.1 mm or more and 0.6 mm or less,
The total number of the plurality of dimples is 200 or more and 500 or less,
The arithmetic average roughness Ra of the surface of the coating layer is 0.5 μm or more and 5.0 μm or less, and the maximum height Rz is 4.0 μm or more,
The surface of the coating layer is rough so that the relationship between the drag coefficient CD1 and the lift coefficient CL1 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2280 rpm satisfies CD1 × CL1 <0.0370. A golf ball is formed. The surface of the coating layer is rough so that the relationship between the drag coefficient CD2 and the lift coefficient CL2 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2940 rpm satisfies CD2 × CL2 <0.0410. The golf ball according to claim 1, wherein the golf ball is formed. A golf ball manufacturing method comprising:
Forming a spherical core;
Covering the core with at least one cover member and forming a plurality of dimples on the cover member constituting the outermost layer;
Coating the cover member constituting the outermost layer with a paint layer;
Roughness is applied to the surface of the coating layer so that the relationship between the drag coefficient CD1 and the lift coefficient CL1 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2280 rpm satisfies CD1 × CL1 <0.0370. Forming step;
With
The golf ball has a diameter of 40 mm or more and 45 mm or less,
The thickness of the coating layer is 5.0 μm or more,
The total volume of the plurality of dimples is 270 mm ³ or more and 370 mm ³ or less,
The surface area occupation ratio by the plurality of dimples is 70% or more and 90% or less,
The depth of each of the plurality of dimples is 0.1 mm or more and 0.6 mm or less,
The total number of the plurality of dimples is 200 or more and 500 or less,
A method for manufacturing a golf ball, wherein an arithmetic average roughness Ra of the surface of the coating layer is 0.5 μm or more and 5.0 μm or less and a maximum height Rz is 4.0 μm or more. In the step of forming the roughness,
Roughness is applied to the surface of the coating layer so that the relationship between the drag coefficient CD2 and the lift coefficient CL2 when hit with a Reynolds number of 1.771 × 10 ⁵ and a spin rate of 2940 rpm satisfies CD2 × CL2 <0.0410. The method for manufacturing a golf ball according to claim 3, wherein the golf ball is formed.