Golf club head

Abstract

To provide a golf club head capable of making repulsion performance and biting feeling compatible.SOLUTION: A golf club head 100 includes a face portion 102 that forms a striking face 102a. The face part 102 has a metallic face part M1 formed of a metallic material and an urethane layer part U1 formed of polyurethane and provided outside the metallic face part U1. In the portion covered with the urethane layer portion U1, the line roughness of the outer surface of the metallic face portion M1 is greater than 4.5 μm in arithmetic average roughness Ra or greater than 25 μm in the maximum height Rz. In the golf club head 100, the line roughness of the outer surface of the metallic face portion M1 may be greater than 4.5 μm in arithmetic average roughness Ra and greater than 25 μm in the maximum height Rz.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a golf club head. [Background technology]

[0002] A variety of materials are used for golf club heads. Composite heads using two or more materials are also known. A material that corresponds to the desired performance of the head can be used.

[0003] Japanese Patent No. 4733336 discloses a golf club head including a body made of a titanium alloy, a striking plate made of a titanium alloy attached to the body, and a thin layer made of thermosetting polyurethane provided on the outer surface of the striking plate, the layer having a thickness in the range of 0.127 to 2.540 mm and including a plurality of scorelines. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4733336 Summary of the Invention [Problem to be solved by the invention]

[0005] The basic performance of a head is its resilience. High resilience can increase the flight distance. On the other hand, high resilience can lead to quick ball release and poor bite. Ball release is the feeling that the ball in contact with the striking surface is released from the striking surface upon impact. Biting is the feeling that the ball does not slide on the striking surface but sticks to it upon impact. It has been difficult to achieve both resilience and good biting.

[0006] An object of the present invention is to provide a golf club head that can achieve both resilience performance and a good biting feel. [Means for solving the problem]

[0007] In one embodiment, the present invention is a golf club head having a face portion forming a striking surface. In this head, the face portion has a metal face portion made of metal and a urethane layer portion made of polyurethane provided on the outside of the metal face portion. In the portion covered with the urethane layer portion, the line roughness of the outer surface of the metal face portion is greater than 4.5 μm in arithmetic mean roughness Ra, or greater than 25 μm in maximum height Rz. Effect of the Invention

[0008] As one aspect, a golf club head can be provided that combines resilience performance with a good biting feel. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view of a golf club head according to the first embodiment. [Diagram 2] FIG. 2 is a bottom view of the golf club head of FIG. [Diagram 3] FIG. 3(a) is a front view of the golf club head of FIG. 1, and FIG. 3(b) is a cross-sectional view of the outer surface of the head taken along line E1 of FIG. 3(a). [Figure 4] FIG. 4 is a perspective view of the golf club head of FIG. [Diagram 5] FIG. 5 is an exploded perspective view of the golf club head of FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. [Figure 7] FIG. 7 is a partially enlarged view of FIG. [Figure 8] FIG. 8 is a plan view of a golf club head according to the second embodiment. [Figure 9] FIG. 9 is a bottom view of the golf club head of FIG. [Figure 10] FIG. 10 is a front view of the golf club head of FIG. [Figure 11]11 is a front view of the head body of the golf club head of FIG. [Figure 12] FIG. 12 is a perspective view of the golf club head of FIG. [Figure 13] 13 is a perspective view of a head body in the golf club head of FIG. 8. FIG. [Figure 14] FIG. 14 is an exploded perspective view of the golf club head of FIG. [Figure 15] FIG. 15 is a cross-sectional view taken along the line AA in FIG. [Figure 16] FIG. 16 is a partially enlarged view of FIG. [Figure 17] FIG. 17 is a plan view of a golf club head according to the third embodiment. [Figure 18] 18 is a bottom view of the golf club head of FIG. [Figure 19] FIG. 19 is a front view of the golf club head of FIG. [Figure 20] 20 is a front view of the head body of the golf club head of FIG. [Figure 21] FIG. 21 is a perspective view of the golf club head of FIG. [Figure 22] 22 is a perspective view of the head body of the golf club head of FIG. 17. FIG. [Diagram 23] 23 is an exploded perspective view of the golf club head of FIG. 17. FIG. [Figure 24] FIG. 24 is a cross-sectional view taken along the line AA in FIG. [Diagram 25] FIG. 25 is a partially enlarged view of FIG. [Figure 26] Figure 26(a) is a front view of a head body of a modified example, Figure 26(b) is a front view of a head body of another modified example, Figure 26(c) is a front view of a head body of another modified example, Figure 26(d) is a front view of a head body of another modified example, and Figure 26(e) is a front view of a head body of another modified example. [Figure 27]FIG. 27(a) is a cross-sectional view of a golf club head according to another modified example, FIG. 27(b) is a cross-sectional view of a golf club head according to another modified example, and FIG. 27(c) is a cross-sectional view of a golf club head according to another modified example. [Figure 28] FIG. 28 is a conceptual diagram for explaining the reference state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0011] In the present application, a reference state, a reference vertical plane, a toe-heel direction, a face-back direction, an up-down direction, a face center, a vertical section, a horizontal section, and a front view are defined.

[0012] A state in which the head is placed on the ground plane HP at a specified lie angle is regarded as a reference state. As shown in FIG. 28, in this reference state, the shaft axis line Z is included in a plane VP perpendicular to the ground plane HP. The shaft axis line Z is the center line of the shaft. Usually, the shaft axis line Z coincides with the center line of the hosel hole. The plane VP is regarded as a reference vertical plane. The specified lie angle is listed, for example, in a product catalog.

[0013] There is known a club in which the loft angle, lie angle, and face angle can be adjusted by the rotational position of a sleeve provided at the tip of the shaft. In this club, the sleeve can be removably fixed to the head by a fixing means such as a screw. Therefore, in this club, the shaft can be attached and detached from the head. In a club having such a detachment mechanism, all adjustment items are neutral in the above-mentioned reference state. Neutral means the center of the adjustment range. A golf club having a head of the present invention may have such a detachment mechanism.

[0014] In this reference state, the face angle is set to 0 degrees. That is, in a plan view seen from above, the normal line at the face center of the striking surface is perpendicular to the toe-heel direction. The face center and the toe-heel direction are defined as described below.

[0015] In this specification, the toe-heel direction is the direction of the intersection line NL between the reference vertical plane VP and the ground plane HP (see FIG. 28). The toe side in the toe-heel direction is also simply called the "toe side". The heel side in the toe-heel direction is also simply called the "heel side".

[0016] In this specification, the face-back direction is a direction perpendicular to the toe-heel direction and parallel to the ground plane HP. The face side in the face-back direction is also simply called the "face side". The back side in the face-back direction is also simply called the "back side".

[0017] In this specification, the vertical direction is a direction perpendicular to the toe-heel direction and perpendicular to the face-back direction. In other words, in this specification, the vertical direction is a direction perpendicular to the ground plane HP. The upper side in the vertical direction is also called the "crown side". The lower side in the vertical direction is also called the "sole side".

[0018] In this specification, the face center is determined as follows. First, an arbitrary point Pr is selected in the vertical direction and the toe-heel direction, which is approximately near the center of the striking surface. Next, a plane is determined that passes through this point Pr, extends along the normal direction of the striking surface at the point Pr, and is parallel to the toe-heel direction. A line of intersection between this plane and the striking surface is drawn, and its midpoint Px is determined. Next, a plane is determined that passes through this midpoint Px, extends along the normal direction of the striking surface at the point Px, and is parallel to the vertical direction. A line of intersection between this plane and the striking surface is drawn, and its midpoint Py is determined. Next, a plane is determined that passes through this midpoint Py, extends along the normal direction of the striking surface at the point Py, and is parallel to the toe-heel direction. A line of intersection between this plane and the striking surface is drawn, and its midpoint Px is newly determined. Next, a plane is determined that passes through this new midpoint Px, extends along the normal direction of the striking surface at the point Px, and is parallel to the vertical direction. A line of intersection between this plane and the striking surface is drawn, and its midpoint Py is newly determined. This process is repeated to sequentially determine Px and Py. In the repetition of this process, the new position Py (last position Py) when the distance between the new midpoint Py and the previous midpoint Py becomes 0.5 mm or less for the first time is the face center.

[0019] In this specification, the longitudinal section is a section taken along a plane perpendicular to the toe-heel direction. In this specification, the transverse section is a section taken along a plane perpendicular to the up-down direction. In other words, in this specification, the transverse section is a section taken along a plane parallel to the ground plane HP.

[0020] In this specification, the front view is a vertical projection of the head obtained by projecting the normal line at the face center. Unless otherwise specified, the shape, area, dimensions, etc. of each region of the face portion are determined in the front view. In this specification, the drawing in the front view is also simply called the front view.

[0021] The plan view of the head 100 is a projection image of the head in a reference state projected onto a plane parallel to the ground plane HP. In this specification, the plan view of the head is also referred to as a planar view.

[0022] FIG. 1 is a plan view of a golf club head 100 of the first embodiment, FIG. 2 is a bottom view of the head 100, FIG. 3(a) is a front view of the head 100, FIG. 3(b) is a cross-sectional line of the outer surface of the head taken along section E1 of FIG. 3(a), FIG. 4 is an oblique view of the head 100, FIG. 5 is an exploded oblique view of the head 100, FIG. 6 is a cross-sectional view taken along line AA of FIG. 3(a), and FIG. 7 is an enlarged partial view of FIG. 6.

[0023] As shown in FIGS. 1 to 7, the head 100 has a face portion 102, a crown portion 104, a sole portion 106, and a hosel portion 108.

[0024] The head 100 may be a wood type. The head 100 may be a hybrid type. The head 100 may be an iron type. The head 100 may be a putter type. In this embodiment, the head 100 is a wood type. The head 100 is a driver head. As shown in FIG. 6, the head 100 has a hollow structure. The head 100 has a hollow portion h.

[0025] As shown in Fig. 6, the face portion 102 forms a hitting surface 102a and a face inner surface 102b. The hitting surface 102a comes into contact with the golf ball when hitting. The hitting surface 102a is the outer surface of the face portion 102. The hitting surface 102a is also simply referred to as the face. The face inner surface 102b is the inner surface of the face portion 102. The face inner surface 102b faces the hollow portion h.

[0026] The crown portion 104 constitutes the upper surface of the head 100. The crown portion 104 forms a crown outer surface 104a and a crown inner surface 104b. The crown inner surface 104b faces the hollow portion h.

[0027] The sole portion 106 constitutes the lower surface of the head 100. The sole portion 106 forms a sole outer surface 106a and a sole inner surface 106b. The sole inner surface 106b faces the hollow portion h.

[0028] The hosel portion 108 is provided on the heel side of the head 100. The hosel portion 108 has a hosel hole 108a. A shaft (not shown) can be inserted into the hosel hole 108a. Alternatively, a sleeve (not shown) attached to the tip of a shaft can be inserted into the hosel hole 108a.

[0029] As shown in FIG. 3(a), the striking face 102a has a face center Fc defined as above.

[0030] The periphery of the striking surface 102a may be defined as follows. As shown in Fig. 3(a), there are many planes E1, E2, E3, etc. that include the normal to the striking surface 102a at the face center Fc. Fig. 3(b) shows the cross-sectional line of the outer surface of the head taken along the plane E1. In the cross-sections of each of these planes E1, etc., a point Q1 is determined where the radius of curvature r of the cross-sectional line of the outer surface of the head first reaches 200 mm from the face center Fc toward the outside of the striking surface 102a. The collection of these points Q1 may be regarded as the periphery of the striking surface 102a.

[0031] As shown in FIG. 1 , the crown portion 104 has a crown protrusion 110. The crown protrusion 110 is a protrusion formed on the crown outer surface 104a. Although not shown, the crown protrusion 110 is a hollow protrusion. Although not shown, a recess is formed on the inner surface of the crown protrusion 110. The crown protrusion 110 can affect the performance of the head 100. For example, the crown protrusion 110 can affect the aerodynamic characteristics of the head 100.

[0032] In the same toe-heel range as the impact area, 45-degree boundary lines are set on the crown side and the sole side. As shown in FIG. 6, a plane tangent to the striking surface 102a at the face center Fc is set as the reference plane S1. In the vertical section, a tangent point P1 between a straight line L1 that forms an angle of 45 degrees with respect to the reference plane S1 and the outer surface of the head is determined. This tangent point P1 can be the outer edge point of the impact area in the vertical section. A vertical section can be set at each position in the toe-heel direction, and a tangent point P1 can be determined in each vertical section. A set of these tangent points P1 is set as the 45-degree boundary line. The impact area is a strip-shaped region centered on a center line that passes through the face center Fc and extends in the up-down direction, and its toe-heel width is 1.68 inches (42.67 mm). This impact area is determined when viewed from the front.

[0033] As shown in FIG. 7, the head 100 has a urethane layer U1. The urethane layer U1 is provided on the face portion 102. The head 100 is composed of a head body 100a and the urethane layer U1. The material of the head body 100a is metal (titanium alloy). The material of the head body 100a is not limited. The head body 100a may be composed of a plurality of materials. The head body 100a may be composed of a plurality of members.

[0034] 7, the face portion 102 has a metal face portion M1 made of metal, and a urethane layer portion U1 provided on the outer side of the metal face portion M1. The urethane layer portion U1 is made of polyurethane.

[0035] The metal face portion M1 has an outer surface 120 and an inner surface 122. The metal face portion M1 is a part of the head body 100a. The inner surface 122 of the metal face portion M1 faces the hollow portion h. The inner surface 122 constitutes the face inner surface 102b. A urethane layer portion U1 is provided on the outer surface 120 of the metal face portion M1. An inner surface 124 of the urethane layer portion U1 is in contact with the outer surface 120. Another layer may be interposed between the outer surface 120 and the urethane layer portion U1. The outer surface 126 of the urethane layer portion U1 is the hitting surface 102a. The metal face portion M1 supports the urethane layer portion U1 from the inside of the head 100.

[0036] The metal face portion M1 may be a layer member that does not belong to the head body 100a. For example, the metal face portion M1 may be disposed between the urethane layer portion U1 and the head body 100a. In this case, the head body 100a located inside the metal face portion M1 may be formed of a metal different from that of the metal face portion M1, or may be formed of a non-metal (such as carbon fiber reinforced plastic).

[0037] The outer surface 120 of the metal face portion M1 has a portion that is covered with the urethane layer portion U1 and a portion that is not covered with the urethane layer portion U1 and is exposed to the outside. In this portion that is exposed to the outside, the metal face portion M1 forms the striking surface 102a. In the portion that is covered with the urethane layer portion U1, the metal face portion M1 does not form the striking surface 102a, but the urethane layer portion U1 forms the striking surface 102a. Note that the entire outer surface 120 of the metal face portion M1 may be covered with the urethane layer portion U1. The urethane layer portion U1 may form the entire striking surface 102a.

[0038] The head main body 100a has a recess 130 for disposing the urethane layer portion U1. The urethane layer portion U1 is disposed in the recess 130. The recess 130 is formed on the outer surface 120 of the metal face portion M1. The contour line 130a of the recess 130 coincides with the contour line k1 of the urethane layer portion U1 (see FIG. 3(a)). The depth of the recess 130 corresponds to the thickness of the urethane layer portion U1. The height of the recess 130 at the contour line 130a coincides with the thickness t of the urethane layer portion U1 at the contour line k1. The bottom surface 130b of the recess 130 is formed by the metal face portion M1. The bottom surface 130b of the recess 130 is the outer surface 120 of the metal face portion M1. The bottom surface 130b of the recess 130 is covered by the urethane layer portion U1. Due to the presence of the recess 130, the striking surface 102a does not substantially have a step (surface step) at the contour line k1 of the urethane layer portion. When the contour line k1 is located within the striking surface 102a, the height of the surface step at the contour line k1 can be set to 0.1 mm or less.

[0039] In this embodiment, the entire urethane layer portion U1 belongs to the face portion 102. The entire urethane layer portion U1 is contained within the striking surface 102a. The urethane layer portion U1 forms part of the striking surface 102a. The striking surface 102a has a portion formed of the urethane layer portion U1 and a portion formed of the metal face portion M1. The portion formed of the metal face portion M1 constitutes the metal striking surface 102c formed of metal. The urethane layer portion U1 is surrounded by the metal striking surface 102c. The urethane layer portion U1 may form the entire striking surface 102a. The contour line k1 of the urethane layer portion U1 may coincide with the contour line of the striking surface 102a.

[0040] In the portion covered with the urethane layer portion U1, the line roughness of the outer surface 120 of the metal face portion M1 satisfies the following (a) and / or (b). In this embodiment, the bottom surface 130b of the recess 130 satisfies the following (a) and / or (b). (a) The arithmetic mean roughness Ra is greater than 4.5 μm. (b) The maximum height Rz is greater than 25 μm.

[0041] The arithmetic mean roughness Ra and maximum height Rz are defined in JIS B 0601:2013 and are measured in accordance with the JIS regulations and JIS B 0633:2001. These values ​​can be measured using a contact or non-contact surface roughness measuring device. For example, these values ​​can be measured using a 3D shape dimension measuring instrument VR-5200 manufactured by Keyence Corporation under the following measurement conditions. When multiple measured values ​​are obtained in the measurement area, the maximum value can be used. Measurement conditions Cutoff value (λc): 0.8mm / 2.5mm / 8mm Filter type: Gaussian λs value: None 3D Measurement Settings: High Precision (Roughness)

[0042] The arithmetic mean roughness Ra and maximum height Rz are set in the portion that constitutes the interface with the urethane layer U1. When the outer surface 120 of the metal face portion M1 has a metal groove, which will be described later with reference to Figures 26(a) to 26(e), the portion in which the metal groove is formed is not the subject for which the arithmetic mean roughness Ra and maximum height Rz are set. The arithmetic mean roughness Ra and maximum height Rz are set in the portion in which the metal groove is not formed.

[0043] In the portion covered with the urethane layer portion U1, the outer surface 120 of the metal face portion M1 satisfies the following (c). (c) The deployment area ratio Sdr is 0.12 or more.

[0044] The above-mentioned development area ratio Sdr is set in the portion constituting the interface with the urethane layer portion U1. When the outer surface 120 of the metal face portion M1 has a metal groove, which will be described later, the portion in which the metal groove is formed is not the target for setting the development area ratio Sdr.

[0045] The developed area ratio Sdr is defined in ISO25178 and is measured in accordance with the ISO standard. The developed area ratio Sdr can be measured, for example, using a non-contact measuring device. The developed area ratio Sdr can be measured, for example, using a 3D shape dimension measuring device VR-5200 manufactured by Keyence Corporation under the following measurement conditions. When multiple measured values ​​are obtained in the measurement area, the maximum value can be used. Measurement conditions Size:10000μm×10000μm Filter type: Gaussian Other filters: None End effect compensation: ON

[0046] In the portion covered with the urethane layer portion U1, the outer surface 120 of the metal face portion M1 may include minute irregularities having a height of 100 nanometers or less. This height is the difference in height between adjacent peaks and valleys. A primer and / or adhesive is provided between the metal face portion M1 and the urethane layer portion U1.

[0047] Figure 8 is a plan view of a golf club head 200 of the second embodiment, Figure 9 is a bottom view of the head 200, Figure 10 is a front view of the head 200, Figure 11 is a front view showing the head 200 with the urethane layer U2 removed, Figure 12 is an oblique view of the head 200, Figure 13 is an oblique view showing the head 200 with the urethane layer U2 removed, Figure 14 is an exploded oblique view of the head 200, Figure 15 is a cross-sectional view along line AA in Figure 10, and Figure 16 is an enlarged partial view of Figure 15.

[0048] 8 to 16, the head 200 has a face portion 202, a crown portion 204, a sole portion 206, and a hosel portion 208. The head 200 is a wood type. As shown in FIG. 15, the head 200 has a hollow structure. The head 200 has a hollow portion h.

[0049] As shown in Fig. 15, the face portion 202 forms a hitting surface 202a and a face inner surface 202b. The hitting surface 202a is the surface that comes into contact with the golf ball when hitting. The hitting surface 202a is the outer surface of the face portion 202. The face inner surface 202b is the inner surface of the face portion 202. The face inner surface 202b faces the hollow portion h. As shown in Fig. 10, the hitting surface 202a has a face center Fc defined as described above.

[0050] As shown in FIG. 15, the crown portion 204 constitutes the upper surface of the head 200. The crown portion 204 forms a crown outer surface 204a and a crown inner surface 204b. The crown inner surface 204b faces the hollow portion h. The crown portion 204 has a crown protrusion 210. The sole portion 206 constitutes the lower surface of the head 200. The sole portion 206 forms a sole outer surface 206a and a sole inner surface 206b. The sole inner surface 206b faces the hollow portion h. The hosel portion 208 is provided on the heel side of the head 200. The hosel portion 208 has a hosel hole 208a.

[0051] 14 and 16, the head 200 has a urethane layer portion U2. The urethane layer portion U2 is provided on the face portion 202. The urethane layer portion U2 forms the entire striking surface 202a. The urethane layer portion U2 extends to the outside of the striking surface 202a. The urethane layer portion U2 extends to the back side of the 45-degree boundary line L2 (see FIG. 6).

[0052] The head 200 is composed of a head body 200a and a urethane layer U2. The material of the head body 200a is metal (titanium alloy). As shown in FIG. 14, the head body 200a is composed of a plurality of members. The head body 200a is composed of a face member 200b and a back member 200c. The back member 200c is joined to the back side of the face member 200b. The face member 200b has a portion that constitutes the face portion 202. The back member 200c has a portion that constitutes the crown portion 204 and a portion that constitutes the sole portion 206. The back member 200c is a member that has an opening 203 on the face side (see FIG. 14). This opening 203 is closed by the face member 200b. The boundary 201 between the face member 200b and the back member 200c is joined by welding. This boundary 201 is located on the contour line of the opening 203.

[0053] 14 and 16, the face portion 202 has a metal face portion M2 made of metal, and a urethane layer portion U2 provided on the outer side of the metal face portion M2. The urethane layer portion U2 is made of polyurethane.

[0054] At least a part of the metal face portion M2 is made up of the face member 200b. In this embodiment, the entire metal face portion M2 is made up of the face member 200b.

[0055] The metal face portion M2 has an outer surface 220 and an inner surface 222. The inner surface 222 of the metal face portion M2 faces the hollow portion h. The inner surface 222 constitutes the face inner surface 202b. A urethane layer portion U2 is provided on the outer surface 220 of the metal face portion M2. An inner surface 224 of the urethane layer portion U2 contacts the outer surface 220. Another layer may be interposed between the outer surface 220 and the urethane layer portion U2. An outer surface 226 of the urethane layer portion U2 forms the hitting surface 202a. The metal face portion M2 supports the urethane layer portion U2 from the inside of the head 200.

[0056] In the head 100 described above, a part of the outer surface 120 of the metal face portion M1 is covered with the urethane layer portion U1. In contrast to this, in the head 200, the entire outer surface 220 of the metal face portion M2 is covered with the urethane layer portion U2. In the completed head 200, the metal face portion M2 is not visible from the outside. The boundary 201 between the face member 200b and the back member 200c is also covered with the urethane layer portion U2. The urethane layer portion U2 extends to the outside of the hitting surface 202a. The urethane layer portion U2 extends to the back side of the 45-degree boundary line L2 (see FIG. 6). The urethane layer portion U2 extends to the crown portion 204. The urethane layer portion U2 extends to the back side of the 45-degree boundary line L2 on the crown side. The urethane layer portion U2 extends to the sole portion 206. The urethane layer portion U2 extends to the back side of the 45-degree boundary line L2 on the sole side.

[0057] The back member 200c has a step portion 228. The step portion 228 is provided at a position corresponding to the rear edge 230 of the urethane layer portion U2. The step portion 228 is provided in the crown portion 204. The step portion 228 is provided in the sole portion 206. The height of the step portion 228 corresponds to the thickness of the urethane layer portion U2 at the rear edge 230. At the boundary k2 between the urethane layer portion U2 and the back member 200c (head body 200a), there is substantially no step (surface step) on the outer surface of the head. In this embodiment, the boundary k2 is located outside the hitting surface 202a. The surface step at the boundary k2 can be 2 mm or less, further 1 mm or less, and further 0.5 mm or less.

[0058] In this embodiment, a portion of the urethane layer portion U2 belongs to the face portion 202. The urethane layer portion U2 forms the entire striking surface 202a. Furthermore, the urethane layer portion U2 extends to the outside of the boundary line of the striking surface 202a. The urethane layer portion U2 extends to the crown portion 204. The urethane layer portion U2 forms part of the crown outer surface 204a. The urethane layer portion U2 extends to the sole portion 206. The urethane layer portion U2 forms part of the sole outer surface 206a.

[0059] As shown in FIG. 16, in the head 200 of the second embodiment, the urethane layer U2 extends to the outside of the hitting surface 202a. The urethane layer U2 extends to the back side of the 45-degree boundary line L2 (see FIG. 6). The head body 200a has an edge fixing portion 234 that fixes the edge portion 232 of the urethane layer U2 on the back side of the 45-degree boundary line L2. The edge fixing portion 234 is located outside the hitting surface 202a. The edge fixing portion 234 is composed of a step portion 228 and the outer surface of the head body 200a in the vicinity of the step portion 228. The edge fixing portion 234 fixes the edge portion 232 of the urethane layer U2 by adhesion.

[0060] In the portion covered with the urethane layer portion U2, the line roughness of the outer surface 220 of the metal face portion M2 satisfies the following (a) and / or (b). (a) The arithmetic mean roughness Ra is greater than 4.5 μm. (b) The maximum height Rz is greater than 25 μm.

[0061] In the portion covered with the urethane layer portion U2, the outer surface 220 of the metal face portion M2 satisfies the following (c). (c) The deployment area ratio Sdr is 0.12 or more.

[0062] In the portion covered with the urethane layer portion U2, the outer surface 220 of the metal face portion M2 includes minute projections and recesses having a height of 100 nanometers or less. A primer and / or an adhesive is provided between the metal face portion M2 and the urethane layer portion U2.

[0063] Figure 17 is a plan view of a golf club head 300 of the third embodiment, Figure 18 is a bottom view of the head 300, Figure 19 is a front view of the head 300, Figure 20 is a front view showing the head 300 with the urethane layer U3 removed, Figure 21 is an oblique view of the head 300, Figure 22 is an oblique view showing the head 300 with the urethane layer U3 removed, Figure 23 is an exploded oblique view of the head 300, Figure 24 is a cross-sectional view along line AA in Figure 19, and Figure 25 is an enlarged partial view of Figure 24.

[0064] 17 to 25, the head 300 has a face portion 302, a crown portion 304, a sole portion 306, and a hosel portion 308. The head 300 is a wood type. As shown in Fig. 24, the head 300 has a hollow structure. The head 300 has a hollow portion h.

[0065] As shown in Fig. 24, the face portion 302 forms a hitting surface 302a and a face inner surface 302b. The hitting surface 302a is the surface that comes into contact with the golf ball when hitting. The hitting surface 302a is the outer surface of the face portion 302. The face inner surface 302b is the inner surface of the face portion 302. The face inner surface 302b faces the hollow portion h. As shown in Fig. 19, the hitting surface 302a has a face center Fc defined as described above.

[0066] The crown portion 304 constitutes the upper surface of the head 300. The crown portion 304 forms a crown outer surface 304a and a crown inner surface 304b. The crown inner surface 304b faces the hollow portion h. The crown portion 304 has a crown protrusion 310. The sole portion 306 constitutes the lower surface of the head 300. The sole portion 306 forms a sole outer surface 306a and a sole inner surface 306b. The sole inner surface 306b faces the hollow portion h. The hosel portion 308 is provided on the heel side of the head 300. The hosel portion 308 has a hosel hole 308a.

[0067] 23 and 25, the head 300 has a urethane layer portion U3. The urethane layer portion U3 is provided on the face portion 302. The urethane layer portion U3 forms the entire striking surface 302a. The urethane layer portion U3 extends to the outside of the striking surface 302a. The urethane layer portion U3 extends to the back side of the 45-degree boundary line L2 (see FIG. 6).

[0068] The head 300 is composed of a head body 300a and a urethane layer U3. The material of the head body 300a is metal (titanium alloy). As shown in FIG. 23, the head body 300a is composed of a plurality of members. The head body 300a is composed of a face member 300b and a back member 300c. The back member 300c is joined to the back side of the face member 300b. The face member 300b has a portion that constitutes the face portion 302. The back member 300c has a portion that constitutes the crown portion 304 and a portion that constitutes the sole portion 306. The back member 300c is a member that has an opening 303 on the face side, and this opening 303 is closed by the face member 300b. The boundary 301 (see FIG. 22) between the face member 300b and the back member 300c is joined by welding.

[0069] 25, the face portion 302 has a metal face portion M3 made of metal, and a urethane layer portion U3 provided on the outer side of the metal face portion M3. The urethane layer portion U3 is made of polyurethane.

[0070] At least a part of the metal face portion M3 is made up of the face member 300b. In this embodiment, the entire metal face portion M3 is made up of the face member 300b.

[0071] The metal face portion M3 has an outer surface 320 and an inner surface 322. The inner surface 322 of the metal face portion M3 faces the hollow portion h. The inner surface 322 constitutes the face inner surface 302b. A urethane layer portion U3 is provided on the outer surface 320 of the metal face portion M3. An inner surface 324 of the urethane layer portion U3 is in contact with the outer surface 320. Another layer may be interposed between the outer surface 320 and the urethane layer portion U3. An outer surface 326 of the urethane layer portion U3 is the hitting surface 302a. The metal face portion M3 supports the urethane layer portion U3 from the inside of the head 300.

[0072] In the head 300, the entire outer surface 320 of the metal face portion M3 is covered with the urethane layer portion U3. In the completed head 300, the metal face portion M3 is not visible from the outside. The boundary 301 between the face member 300b and the back member 300c is also covered with the urethane layer portion U3. The urethane layer portion U3 extends to the outside of the hitting surface 302a. The urethane layer portion U3 extends to the back side of the 45-degree boundary line L2 (see FIG. 6). The urethane layer portion U3 extends to the crown portion 304. The urethane layer portion U3 extends to the back side of the 45-degree boundary line L2 on the crown side. The urethane layer portion U3 extends to the sole portion 306. The urethane layer portion U3 extends to the back side of the 45-degree boundary line L2 on the sole side.

[0073] As shown in FIG. 25, the head body 300a has a groove 328. The groove 328 is provided on the outer side of the hitting surface 302a. The groove 328 is provided in the back member 300c. The groove 328 is provided at a position corresponding to the edge (rear edge) 330 of the urethane layer portion U3. The groove 328 is provided in the crown portion 304. The groove 328 is provided in the sole portion 306. The edge 330 of the urethane layer portion U3 is bent in a direction toward the inside of the head 300. The extension direction of the edge 330 coincides with the depth direction of the groove 328. The width of the groove 328 corresponds to the thickness of the edge 330. The edge 330 enters the groove 328. The groove 328 is filled with the edge 330.

[0074] At the boundary k3 between the urethane layer U3 and the back member 300c (head body 300a), there is substantially no step (surface step) on the outer surface of the head. The boundary k3 is located outside the striking surface 302a. The surface step at the boundary k3 can be 2 mm or less, further 1 mm or less, or further 0.5 mm or less.

[0075] In this embodiment, a portion of the urethane layer portion U3 belongs to the face portion 302. The urethane layer portion U3 forms the entire striking surface 302a. The urethane layer portion U3 extends to the crown portion 304. The urethane layer portion U3 forms a portion of the crown outer surface 304a. The urethane layer portion U3 extends to the sole portion 306. The urethane layer portion U3 forms a portion of the sole outer surface 306a.

[0076] As shown in FIG. 25, in the head 300 of the third embodiment, the urethane layer U3 also extends to the outside of the hitting surface 302a. The urethane layer U3 extends to the back side of the 45-degree boundary line L2 (see FIG. 6). The head body 300a has an edge fixing portion 334 that fixes the edge portion 330 of the urethane layer U3 on the back side of the 45-degree boundary line L2. The edge fixing portion 334 is located outside the hitting surface 302a. In this embodiment, the edge fixing portion 334 is a groove 328. The edge fixing portion 334 is provided in the crown portion 304. The edge fixing portion 334 is provided in the sole portion 306. The groove 328 (edge ​​fixing portion 334) physically locks the edge portion 330. Furthermore, the edge portion 330 is fixed to the groove 328 (edge ​​fixing portion 334) by adhesion. The thickness t of the urethane layer U3 in the striking surface 302a region is smaller than the thickness t of the urethane layer U3 in the edge 330. That is, the thickness t of the urethane layer U3 in the edge 330 is larger than the thickness t of the urethane layer U3 in the striking surface 302a region. This thickness t is measured along the normal direction of the outer surface of the head 300. The layer thickness v of the urethane layer U3 in the edge 330 is larger than the layer thickness v of the urethane layer U3 in the striking surface 302a region. This layer thickness v is measured along the direction in which the thickness is minimum in the longitudinal section (see FIG. 25).

[0077] In the portion covered with the urethane layer portion U3, the line roughness of the outer surface 320 of the metal face portion M3 satisfies the following (a) and / or (b). (a) The arithmetic mean roughness Ra is greater than 4.5 μm. (b) The maximum height Rz is greater than 25 μm.

[0078] In the portion covered with the urethane layer portion U3, the outer surface 320 of the metal face portion M3 satisfies the following (c). (c) The deployment area ratio Sdr is 0.12 or more.

[0079] In the portion covered with the urethane layer portion U3, the outer surface 320 of the metal face portion M3 may include minute irregularities having a height of 100 nanometers or less. A primer and / or an adhesive is provided between the metal face portion M3 and the urethane layer portion U3.

[0080] 26(a) to (e) are front views of the head body of the head of the modified example. These show the head with the urethane layer removed. The metal grooves in these modified examples can be applied to the heads of the first to third embodiments described above.

[0081] FIG. 26(a) is a front view of the head body 400a in the head 400 according to the modified example. In other words, FIG. 26(a) is a front view of the head 400 with the urethane layer removed. The head body 400a has a metal face portion M4. In the portion covered with the urethane layer, the outer surface 420 of the metal face portion M4 may have one or more grooves. In this embodiment, the outer surface 420 has a plurality of grooves s4. In order to distinguish from other grooves, in this specification, the groove s4 provided on the outer surface 420 of the metal face portion M4 is also referred to as a metal groove. Since the metal groove s4 is covered with the urethane layer, it is not visible from the outside of the head 400. Of course, this is the case when the urethane layer does not have transparency. The urethane layer may have transparency. That is, the urethane layer may be transparent or translucent. In this case, the metal groove s4 can be visible from the outside.

[0082] The outer surface 420 of the metal face portion M4 has a central region 440 that does not have a metal groove s4, a toe groove region 442 located on the toe side of the central region 440 and in which the metal groove s4 is arranged, and a heel groove region 444 located on the heel side of the central region 440 and in which the metal groove s4 is arranged. In a front view, the central region 440 includes the position of the face center Fc in a front view.

[0083] The metal face portion M4 has a hitting surface portion 446 that is covered with a portion of the urethane layer that constitutes the hitting surface. A central region 440, a toe groove region 442, and a heel groove region 444 are provided in the hitting surface portion 446. The central region 440 traverses the hitting surface portion 446 from the crown side to the sole side.

[0084] Each of the metal grooves s4 extends in a vertical direction. The vertical direction may be a direction that forms an angle of ±20° or less with respect to the up-down direction when viewed from the front. The metal grooves s4 extend in the vertical direction outside the impact area. In the metal face portion M4, the density of the metal grooves s4 is higher outside the impact area than inside the impact area.

[0085] Fig. 26(b) is a front view of a head body 500a of a head 500 according to another modified example. In other words, Fig. 26(b) is a front view of the head 500 with the urethane layer removed. The head body 500a has a metal face portion M5. In the portion covered with the urethane layer, the outer surface 520 of the metal face portion M5 has a plurality of grooves (metal grooves) s5. The metal grooves s5 are covered with the urethane layer. If this urethane layer is not transparent, the metal grooves s5 in the head 500 will not be visible from the outside.

[0086] The outer surface 520 of the metal face portion M5 has a central region 540 that does not have a metal groove s5, a toe groove region 542 located on the toe side of the central region 540 and in which the metal groove s5 is arranged, a heel groove region 544 located on the heel side of the central region 540 and in which the metal groove s5 is arranged, an upper groove region 550 located on the upper side of the central region 540 and in which the metal groove s5 is arranged, and a lower groove region 552 located on the lower side of the central region 540 and in which the metal groove s5 is arranged. In a front view, the central region 540 includes the position of the face center Fc.

[0087] The metal face portion M5 has a striking surface portion 546 that is covered with a portion of the urethane layer that constitutes the striking surface. The striking surface portion 546 is provided with a central region 540, a toe groove region 542, a heel groove region 544, an upper groove region 550, and a lower groove region 552.

[0088] In the toe groove region 542 and the heel groove region 544, each of the metal grooves s5 extends in the vertical direction. In the upper groove region 550 and the lower groove region 552, each of the metal grooves s5 extends in the horizontal direction. The horizontal direction may be a direction that forms an angle of ±20° or less with respect to the toe-heel direction in a front view. The metal grooves s5 are disposed in the vertical direction on the outside of the impact area. The metal grooves s5 are disposed in the horizontal direction on the inside of the impact area. The directions of the metal grooves s5 are different between the inside and outside of the impact area.

[0089] Fig. 26(c) is a front view of a head body 600a of a head 600 according to another modified example. In other words, Fig. 26(c) is a front view of the head 600 with the urethane layer removed. The head body 600a has a metal face portion M6. In the portion covered with the urethane layer, the outer surface 620 of the metal face portion M6 has a plurality of grooves (metal grooves) s6. The metal grooves s6 are covered with the urethane layer. If this urethane layer is not transparent, the metal grooves s6 in the head 600 will not be visible from the outside.

[0090] The outer surface 620 of the metal face portion M6 has a central region 640 that does not have a metal groove s6, a toe groove region 642 located on the toe side of the central region 640 and in which the metal groove s6 is arranged, and a heel groove region 644 located on the heel side of the central region 640 and in which the metal groove s6 is arranged. In a front view, the central region 640 includes the face center.

[0091] The metal face portion M6 has a hitting surface portion 646 that is covered with a portion of the urethane layer portion that constitutes the hitting surface. A central region 640, a toe groove region 642, and a heel groove region 644 are provided in the hitting surface portion 646. The central region 640 traverses the hitting surface portion 646 from the crown side to the sole side.

[0092] In the toe groove region 642, each of the metal grooves s6 extends in a curved manner so as to be convex toward the toe side. In the heel groove region 644, each of the metal grooves s6 extends in a curved manner so as to be convex toward the heel side. In the metal face portion M6, the density of the metal grooves s6 is higher on the outside of the impact area than on the inside of the impact area.

[0093] Fig. 26(d) is a front view of a head body 700a of a head 700 according to another modified example. In other words, Fig. 26(d) is a front view of the head 700 with the urethane layer removed. The head body 700a has a metal face portion M7. In the portion covered with the urethane layer, the outer surface 720 of the metal face portion M7 has a plurality of grooves (metal grooves) s7. The metal grooves s7 are covered with the urethane layer. If this urethane layer is not transparent, the metal grooves s7 in the head 700 will not be visible from the outside.

[0094] The outer surface 720 of the metal face portion M7 does not have a central region that does not have metal grooves s7. The metal grooves s7 are arranged over the entire outer surface 720. The metal face portion M7 has a striking surface portion 746 that is covered by a portion of the urethane layer that constitutes the striking surface. All of the metal grooves s7 are arranged in the striking surface portion 746. Each of the metal grooves s7 extends in the lateral direction. The lateral direction may be defined as a direction that forms an angle of ±20° or less with respect to the toe-heel direction when viewed from the front.

[0095] FIG. 26(e) is a front view of the head body 800a in the head 800 according to another modified example. In other words, FIG. 26(e) is a front view of the head 800 with the urethane layer removed. The head body 800a has a metal face portion M8. In the portion covered with the urethane layer, the outer surface 820 of the metal face portion M8 has a plurality of grooves (metal grooves) s8. The metal grooves s8 are covered with the urethane layer. If the urethane layer is not transparent, the metal grooves s8 are not visible from the outside in the head 800. The metal face portion M7 has a striking surface portion 846 that is covered with a portion of the urethane layer that constitutes the striking surface. All the metal grooves s8 are arranged in the striking surface portion 846. Each of the metal grooves s8 extends along a circle centered on a predetermined point. This center point may be located at the face center Fc or in its vicinity. The position of this central point can be within a circle of radius r centered on the face center Fc in a front view, and this radius r can be set to 22 mm, further 16 mm, or further 10 mm.

[0096] The urethane layer may have one or more grooves on its outer surface. To distinguish from other grooves, this groove is also called a urethane groove. The urethane groove is provided in an area that constitutes the striking surface. This urethane groove is a groove provided on the striking surface, and can be a so-called face groove (score line). Note that in the following embodiment, a urethane groove and a metal groove are provided, but a urethane groove may be provided without a metal groove.

[0097] FIG. 27(a) is a vertical cross-sectional view of a modified example having a urethane groove. The head of this modified example is obtained by adding a urethane layer U7 to the head body 700a (FIG. 26(d)) described above. The urethane layer U7 has a groove g7. The groove provided in the urethane layer U7 is also called a urethane groove. The urethane groove g7 is provided on the striking surface 702a. The urethane groove g7 extends in the lateral direction. The urethane groove g7 extends parallel to the metal groove s7. One urethane groove g7 is provided between two adjacent metal grooves s7. The urethane groove g7 and the metal groove s7 are alternately arranged. The urethane groove g7 is provided at a position that does not overlap the metal groove s7. The urethane groove g7 can be provided in compliance with the golf rules regarding grooves in the impact area.

[0098] The urethane layer portion U7 has a convex portion 750 on its inner surface 724. This convex portion 750 is also referred to as an inner surface convex portion. The inner surface 724 of the urethane layer portion U7 has an inner surface convex portion 750. The inner surface convex portion 750 fits into the metal groove s7. The height of the inner surface convex portion 750 is equal to the depth of the metal groove s7. The width of the inner surface convex portion 750 is equal to the width of the metal groove s7. The inner surface convex portion 750 fills the metal groove s7. The inner surface convex portion 750 is provided at a position that does not overlap the metal groove s7. The inner surface convex portion 750 may be inserted into the metal groove s7 after being formed in advance in the urethane layer portion U7, or may be formed by the metal groove s7.

[0099] Fig. 27(b) is a vertical cross-sectional view of another modified example. The only difference between the embodiment in Fig. 27(b) and the embodiment in Fig. 27(a) is the depth of the metal groove s7 (and the height of the inner surface convex portion 750). In this embodiment, the depth of the metal groove s7 differs among the multiple metal grooves s7. The depth of the metal groove s7 is smaller the closer to the face center Fc. In other words, the depth of the metal groove s7 is larger the farther from the face center Fc. This configuration may be suitable for golfers who often hit off-center, such as average golfers.

[0100] FIG. 27(c) is a vertical cross-sectional view of another modified example. The only difference between the embodiment in FIG. 27(c) and the embodiment in FIG. 27(a) is the depth of the metal groove s7 (and the height of the inner surface convex portion 750). In this embodiment, the depth of the metal groove s7 differs among the multiple metal grooves s7. The depth of the metal groove s7 is greater the closer it is to the face center Fc. In other words, the depth of the metal groove s7 is smaller the farther it is from the face center Fc. This configuration may be suitable for golfers who often hit the ball near the face center Fc, such as advanced golfers and professional golfers.

[0101] The embodiment of Figures 27(a) to (c) is a modified example using the head body 700a of Figure 26(d), but the configuration having an inner convex portion that fits into the metal groove can be applied to metal grooves of any configuration, including the embodiments of Figures 26(a) to (e).

[0102] The above-described embodiments can provide the following advantages.

[0103] By providing a metal face portion, the structural portion of the head, including the face portion, can be formed of metal, and thus the repulsion performance can be improved. On the other hand, a metal head with high repulsion performance has a tendency for the ball to leave the ball quickly and to slip easily, making it difficult to obtain a good feeling of bite. That is, in this case, the ball is likely to leave the striking surface quickly and to slip easily on the striking surface at the time of impact. As a result, the maneuverability is likely to decrease. Also, if the ball leaves the striking surface quickly, the hitting feeling may feel hard. Note that maneuverability means the ability to intentionally control the hit ball. If the maneuverability is not good, the probability of hitting a shot with the intended trajectory may decrease.

[0104] By providing a urethane layer on the metal face, it is possible to improve the biting feeling in a head with a metal structure having high resilience performance. By providing a urethane layer on the outside of the metal face and increasing the surface roughness of the metal face at the interface between the metal face and the urethane layer, it is possible to enhance the biting feeling. Although it is difficult to objectively measure this biting feeling, golfers (especially advanced golfers and professional golfers) can recognize it as a hitting feeling.

[0105] During impact, the urethane layer easily adheres to the ball cover, which is made of the same resin. This effectively prevents the ball from slipping on the striking surface during impact. This results in a better grip and improved maneuverability.

[0106] If the cover material of the ball is polyurethane, the adhesion between the urethane layer and the cover of the ball is further increased, which can improve the feeling of biting. Advanced golfers and professional golfers in particular tend to use balls with a polyurethane cover material.

[0107] Increasing the surface roughness of the metal face creates an anchor effect for the urethane layer, making the urethane layer less likely to slip against the metal face upon impact and improving the feeling of grip.

[0108] The anchor effect of the surface roughness of the metal face can reach the ball through the urethane layer. The strong pressure of the impact compresses the urethane layer, and the unevenness of the metal surface can be reflected on the striking surface. This further enhances the feeling of grip.

[0109] The anchor effect of the surface roughness of the metal face increases the adhesion of the urethane layer to the metal face. This effectively prevents the urethane layer from slipping or coming off. The use of an adhesive and / or primer further increases the adhesion of the urethane layer to the metal face.

[0110] The surface area of ​​the metal face portion is increased by the surface roughness or the developed area ratio, and the bonding area is increased. This further improves the adhesion of the urethane layer to the metal face portion. The surface area of ​​the metal face portion is further increased by the fine irregularities having a height of 100 nanometers or less, and the adhesion is further improved.

[0111] When the ball hits the metal face, which has high resilience, the impact feels hard. The urethane layer placed on the outer surface of the metal face provides a good impact feel.

[0112] In the head 200 of the second embodiment, the urethane layer U2 extends to the outside of the hitting surface 202a, and an edge 232 of the urethane layer U2 is fixed by an edge fixing part 234 located on the outside of the hitting surface 202a. In this configuration, as long as the ball hits the hitting surface 202a, the ball does not hit the edge 232. When the ball hits the edge of the urethane layer U2, the urethane layer around the impact point becomes insufficient, and the adhesive strength against the shear force decreases. Since the edge 232 is located on the outside of the hitting surface 202a, the ball is less likely to hit it, and the adhesive strength is less likely to become insufficient. As a result, the adhesive strength of the urethane layer U2 is increased.

[0113] In the head 300 of the third embodiment, the edge fixing portion 334 provided on the outer side of the striking surface 302a is a groove 328. The edge portion 330 is physically locked by being inserted into this groove 328. In this embodiment, the effect of the edge fixing portion 334 arranged on the outer side of the striking surface 302a is further enhanced. The edge fixing portion 334 may sandwich the edge portion 330. For example, the edge portion 330 may be inserted into the groove 328 while being compressed.

[0114] As shown in Figures 26(a) to (e), heads 400 to 800 are provided with metal grooves. These metal grooves have an edge effect that suppresses slippage of the urethane layer against the metal face. Furthermore, the edge effect of the metal grooves can reach the ball through the urethane layer. The strong pressing force at impact compresses the urethane layer, and the edge effect of the metal grooves can be reflected on the striking surface. This can further improve the feeling of bite.

[0115] As shown in Figures 26(a) to (e), heads 400 to 800 are provided with metal grooves s4 to s8. These metal grooves suppress slippage of the urethane layer against the metal face due to their edge effect. The strong pressing force at the time of impact compresses the urethane layer and bites into the metal grooves, enhancing the edge effect. The metal grooves increase the adhesion strength of the urethane layer against shear forces.

[0116] As in the embodiments of Figures 26(a), (b) and (c), the metal grooves can be selectively (or densely) arranged on the peripheral side of the striking surface. As described above, when a ball strikes the edge of the urethane layer, the adhesion strength against shear force is likely to be insufficient. The metal grooves arranged on the peripheral side can effectively increase the adhesion strength when the ball strikes the edge of the urethane layer. Also, as shown in Figures 26(a) to (e), the orientation of the metal grooves can be arranged so as to be approximately perpendicular to the direction of the shear force due to the strike. This configuration can increase the adhesion strength against shear force.

[0117] As shown in Fig. 27(a) to (c), when an inner surface protrusion 750 that enters the metal groove s7 is provided, the inner surface protrusion 750 engages with the metal groove s7, and the adhesion strength against shearing force is further increased. In addition, the urethane groove g7 is provided at a position that does not overlap with the metal groove s7, so that the function of the urethane groove g7 as a face groove is prevented from being deteriorated. As shown in Fig. 27(b), the metal groove s7 may become deeper as it moves away from the face center Fc, and in this case, the adhesion strength on the peripheral side of the striking surface can be effectively increased. As shown in Fig. 27(c), the metal groove s7 may become deeper as it moves closer to the face center Fc, and in this case, the adhesion strength at the face center Fc where the striking frequency is high can be effectively increased.

[0118] From the viewpoint of the bite feeling, the arithmetic mean roughness Ra of the outer surface of the metal face part in the part covered with the urethane layer part is preferably larger than 4.5 μm, more preferably 7 μm or more, and more preferably 10 μm or more. From the viewpoint of the fixing strength, it is preferable that the arithmetic mean roughness Ra is large. If the arithmetic mean roughness Ra is too large, the unevenness of the metal face part may be excessively reflected on the striking surface through the urethane layer part. In this case, the contact relationship between the unevenness and the dimples of the ball may affect the movement of the ball. From this viewpoint, the arithmetic mean roughness Ra is preferably 100 μm or less, more preferably 90 μm or less, and more preferably 80 μm or less.

[0119] It is preferable that the arithmetic mean roughness Ra, which is the line roughness, satisfies the above-mentioned preferable numerical range in both the longitudinal direction and the transverse direction, in which case the adhesive strength against the shear forces in the longitudinal and transverse directions can be increased.

[0120] From the viewpoint of the bite feeling, the maximum height Rz of the outer surface of the metal face part in the part covered with the urethane layer part is preferably larger than 25 μm, more preferably 40 μm or more, and more preferably 60 μm or more. From the viewpoint of the fixing strength, the maximum height Rz is preferably large. If this maximum height Rz is too large, the unevenness of the metal face part may be excessively reflected on the striking surface through the urethane layer part. In this case, the contact relationship between the unevenness and the dimples of the ball may affect the movement of the ball. From this viewpoint, the maximum height Rz is preferably 400 μm or less, more preferably 390 μm or less, and more preferably 380 μm or less.

[0121] It is preferable that the maximum height Rz, which is the line roughness, satisfies the above-mentioned preferable numerical range in both the longitudinal direction and the transverse direction, in which case the adhesive strength against shear forces in the longitudinal and transverse directions can be increased.

[0122] From the viewpoint of the bite feeling, the developed area ratio Sdr of the outer surface of the metal face part in the part covered with the urethane layer is preferably 0.12 or more, more preferably 0.2 or more, and more preferably 0.25 or more. From the viewpoint of the fixing strength, it is preferable that the developed area ratio Sdr is large. Considering the preferable upper limit values ​​of the arithmetic mean roughness Ra and the maximum height Rz, this developed area ratio Sdr is preferably 10 or less, more preferably 9 or less, and more preferably 8 or less.

[0123] From the standpoint of bite feeling, the outer surface of the metal face portion in the portion covered with the urethane layer may satisfy the following (d). From the standpoint of adhesive strength, this (d) may also be satisfied. (d) Sdr≧0.02331Ra+0.07 In this formula, Sdr is the developed area ratio described above, and Ra is the arithmetic mean roughness described above.

[0124] From the standpoint of bite feeling, the outer surface of the metal face portion in the portion covered with the urethane layer may satisfy the following (e). From the standpoint of adhesive strength, this (e) may also be satisfied. (e) The arithmetic mean roughness Ra is greater than 4.5 and the developed area ratio Sdr is greater than 0.07.

[0125] From the standpoint of bite, the outer surface of the metal face portion in the portion covered with the urethane layer may satisfy the following (f). From the standpoint of adhesion strength, this (f) may also be satisfied. (f) Sdr≧0.0049Rz+0.05 In this formula, Sdr is the developed area ratio described above, and Rz is the maximum height roughness.

[0126] From the viewpoint of suppressing slippage of the urethane layer and enhancing the bite feeling, the depth of the metal groove is preferably 0.1 mm or more, more preferably 0.15 mm or more, and more preferably 0.2 mm or more. From the viewpoint of adhesion strength, the depth of the metal groove is preferably large. From the viewpoint of strength of the metal face portion, the depth of the metal groove is preferably 2 mm or less, more preferably 1.9 mm or less, and more preferably 1.8 mm or less. The depth of the metal groove is measured along the direction perpendicular to the striking surface.

[0127] From the viewpoint of suppressing slippage of the urethane layer and enhancing the bite feeling, the width of the metal groove is preferably 0.5 mm or more, more preferably 0.75 mm or more, and more preferably 1 mm or more. From the viewpoint of adhesion strength, the width of the metal groove is preferably made large. From the viewpoint of the strength of the metal face portion, the width of the metal groove is preferably 6 mm or less, more preferably 5.5 mm or less, and more preferably 5 mm or less. The width of the metal groove is measured by the 30-degree measurement method (R&A and USGA test internal regulations), which is a method for measuring the width of the groove in the impact area of ​​the striking surface. Note that the metal groove is not a groove on the striking surface, and is not bound by the golf rules. Therefore, the metal groove may extend along a curve, for example, the width of the bottom of the groove may be larger than the opening width of the groove, or the cross-sectional shape may be asymmetric. The intervals between the multiple metal grooves may not be consistent. The cross-section of the metal groove may not be consistent. The cross-sectional area of ​​the metal groove may be freely set.

[0128] The adhesive may preferably be one that has excellent bonding strength between the urethane layer and the metal face. For example, the trade names "Chemlock 218E", "Chemlock 210" and "Chemlock IMB1040" manufactured by Lord Japan Co., Ltd. may be used as this adhesive ("Chemlock" is a registered trademark). Other adhesives include, for example, the trade names "Metalock C-12" and "Metalock UA" manufactured by Toyo Kagaku Kenkyusho Co., Ltd. ("Metalock" is a registered trademark). Other adhesives include, for example, two-liquid mixed epoxy adhesives. For example, the two-liquid mixed epoxy adhesives are commercially available from 3M Japan Co., Ltd. under the trade names "DP420" and "DP460".

[0129] The method for forming the urethane layer is not limited. For example, the urethane layer may be molded separately from the head body and then attached to the head body. For example, the urethane layer may be molded on the head body in a mold. The urethane layer may be a coating film. The urethane layer may be formed on the head body by, for example, the following method. (1) A molded body for the urethane layer is prepared separately from the head body, and this molded body is attached to the surface of the head with an adhesive. (2) A temporary molded body of the urethane layer portion is prepared separately from the head body, a primer is applied to the portion of the metal face portion where the urethane layer portion is to be placed, the temporary molded body placed on the primer of the metal face portion is set in a mold, and the temporary molded body is heated and melted within the mold to form the urethane layer portion. (3) Unreacted urethane raw material is poured into the mold with the metal face portion set in it and allowed to react, forming a urethane layer on the metal face portion. (4) Thermoplastic polyurethane is injection molded (insert molded) into the mold in which the metal face portion is set, to form a urethane layer portion on the metal face portion.

[0130] The method for roughening the outer surface of the metal face portion is not limited. The outer surface of the metal face portion may be roughened by molding using a mold, or by surface processing. Examples of surface processing methods include blast processing such as shot blasting and sand blasting, metal etching, CNC processing, laser processing, and combinations thereof. CNC is an abbreviation for Computerized Numerical Control.

[0131] In Fig. 7, Fig. 16, Fig. 25 and Fig. 27(a), the thickness of the urethane layer is indicated by a double-headed arrow t. From the viewpoint of the bite feeling, the thickness t of the urethane layer in the striking surface region is preferably 0.3 mm or more, more preferably 0.32 mm or more, and more preferably 0.35 mm or more. If the thickness t is too large, the unevenness of the metal face portion will be difficult to reach the ball, and the bite feeling may be reduced. From this viewpoint, the thickness t of the urethane layer in the striking surface region is preferably 0.8 mm or less, more preferably 0.7 mm or less, and more preferably 0.6 mm or less. From the viewpoint of the resilience performance, it is preferable that the thickness t is small. The thickness t of the urethane layer in the striking surface region is measured at a position where the urethane groove g7 does not exist (see Fig. 27(a)). The thickness t of the urethane layer in the striking surface region is measured at a position where the inner surface convex portion 750 does not exist.

[0132] The urethane layer is made of polyurethane. Polyurethane is a polymer having urethane bonds. Examples of this polyurethane include thermoplastic polyurethane and thermosetting polyurethane. Thermoplastic polyurethane is a polyurethane that exhibits plasticity when heated. In general, thermoplastic polyurethane means polyurethane having a linear structure that has been molecular weighted to a certain degree. Thermosetting polyurethane is a polyurethane obtained by reacting a low molecular weight urethane prepolymer with a curing agent (chain extender) to increase the molecular weight when forming the urethane layer. Thermosetting polyurethane is also called two-component curing polyurethane. Thermosetting polyurethane includes polyurethane having a linear structure and polyurethane having a three-dimensional crosslinking structure, which can be produced by controlling the number of functional groups of the prepolymer and curing agent (chain extender) used. Polyurethane may be a thermoplastic elastomer.

[0133] The thermoplastic polyurethane is not particularly limited as long as it has a plurality of polyurethane bonds in the molecule and exhibits thermoplasticity. For example, the thermoplastic polyurethane is a product in which urethane bonds are formed in the molecule by reacting polyisocyanate with polyol, and can be obtained by further reacting with polyamine, etc., as necessary.

[0134] The polyisocyanate component constituting the thermoplastic polyurethane is not particularly limited as long as it has two or more isocyanate groups, and examples thereof include aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitrylene-4,4'-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and paraphenylene diisocyanate (PPDI); 4,4'-dicyclohexylmethane diisocyanate (H 12MDI), hydrogenated xylylene diisocyanate (H 6 The isocyanate may be one of alicyclic polyisocyanates or aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), norbornene diisocyanate (NBDI), or a mixture of two or more of them.

[0135] From the viewpoint of improving the abrasion resistance, it is preferable to use an aromatic polyisocyanate as the polyisocyanate component of the polyurethane. By using an aromatic polyisocyanate, the mechanical properties of the resulting polyurethane are improved, and a urethane layer portion having excellent abrasion resistance is obtained. In addition, from the viewpoint of improving the weather resistance, it is preferable to use a non-yellowing polyisocyanate (TMXDI, XDI, HDI, H 6 XDI, IPDI, H 12 It is preferable to use 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI) is used. 4,4'-Dicyclohexylmethane Diisocyanate (H 12 MDI) has a rigid structure, which improves the mechanical properties of the resulting polyurethane and provides a urethane layer with excellent abrasion resistance. From the viewpoint of improving the bite, other polyisocyanate components may be selected.

[0136] The polyol component constituting the thermoplastic polyurethane is not particularly limited as long as it has a plurality of hydroxyl groups, and examples thereof include low molecular weight polyols and high molecular weight polyols. Examples of low molecular weight polyols include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; and triols such as glycerin, trimethylolpropane, and hexanetriol. Examples of high molecular weight polyols include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); condensation polyester polyols such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA); lactone polyester polyols such as poly-ε-caprolactone (PCL); polycarbonate polyols such as polyhexamethylene carbonate; and acrylic polyols, and may be a mixture of at least two of the above-mentioned polyols.

[0137] The average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 400 or more, more preferably 1,000 or more. If the average molecular weight of the high molecular weight polyol is too small, the polyurethane obtained may become hard and the hitting feeling may be deteriorated. The upper limit of the average molecular weight of the high molecular weight polyol is not particularly limited, but is 10,000 or less, more preferably 8,000 or less.

[0138] The polyamine constituting the thermoplastic polyurethane as required is not particularly limited as long as it has at least two amino groups. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine, alicyclic polyamines such as isophoronediamine and piperazine, and aromatic polyamines.

[0139] The aromatic polyamine is not particularly limited as long as at least two or more amino groups are directly or indirectly bonded to the aromatic ring.Here, "indirectly bonded" means that the amino group is bonded to the aromatic ring via, for example, a lower alkylene group.The aromatic polyamine may be, for example, a monocyclic aromatic polyamine having two or more amino groups bonded to one aromatic ring, or a polycyclic aromatic polyamine having two or more aminophenyl groups, in which at least one amino group is bonded to one aromatic ring.

[0140] Examples of the monocyclic aromatic polyamine include phenylenediamine, toluenediamine, diethyltoluenediamine, dimethylthiotoluenediamine, and the like, in which an amino group is directly bonded to an aromatic ring; and xylylenediamine, in which an amino group is bonded to an aromatic ring via a lower alkylene group. The polycyclic aromatic polyamine may be a poly(aminobenzene) in which at least two aminophenyl groups are directly bonded, or may be bonded via a lower alkylene group or an alkylene oxide group. Among these, diaminodiphenylalkanes in which two aminophenyl groups are bonded via a lower alkylene group are preferred, and 4,4'-diaminodiphenylmethane and its derivatives are particularly preferred.

[0141] The composition of the thermoplastic polyurethane is not particularly limited. Examples of the composition include a composition composed of a polyisocyanate component and a high molecular weight polyol component, a composition composed of a polyisocyanate component, a high molecular weight polyol component, and a low molecular weight polyol component, a composition composed of a polyisocyanate component, a high molecular weight polyol component, a low molecular weight polyol component, and a polyamine component, and a composition composed of a polyisocyanate component, a high molecular weight polyol component, and a polyamine component.

[0142] Examples of the thermoplastic polyurethane include MDI-based polyurethane in which MDI is used as the polyisocyanate, and H 12 Hydrogenated MDI-based polyurethanes using MDI are also included.

[0143] Specific examples of the thermoplastic polyurethane include "Elastollan XNY90A", "Elastollan XNY97A", ​​"Elastollan XNY585", "Elastollan 1180A10", "Elastollan 1185A50", "Elastollan 1190A10TR", "Elastollan 1195A50STR", and "Elastollan 1164D50", all of which are commercially available from BASF Japan Ltd.

[0144] In the present invention, the material of the urethane layer is not particularly limited as long as it contains polyurethane as a base resin component. When the polyurethane is a thermoplastic polyurethane, the content of the thermoplastic polyurethane in the resin component constituting the urethane layer material is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. In another preferred embodiment, the resin component constituting the urethane layer material is substantially composed of polyurethane only (for example, thermoplastic polyurethane only).

[0145] In addition to the above-mentioned resin components, the urethane layer material of the present invention may contain pigment components such as white pigments (e.g., titanium oxide), blue pigments, and red pigments, specific gravity adjusters such as calcium carbonate and barium sulfate, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, or fluorescent brighteners, within the range that does not excessively impair the performance of the urethane layer.

[0146] The Shore D hardness of the striking surface is not limited. From the viewpoint of hitting feeling, this Shore D hardness can be set to a predetermined range. The lower limit of the Shore D hardness of the striking surface can be 65 or more, further 70 or more, and further 75 or more. The upper limit of the Shore D hardness of the striking surface can be 99 or less, further 95 or less, and further 90 or less.

[0147] The Shore D hardness of the striking surface is measured in the completed head state. The head is stored at 23°C for two weeks, and the hardness of the striking surface of this head is measured using an Asker rubber hardness tester type D. The measurement is performed by pressing the hardness tester against the striking surface of the head. The number of measurements is set to 10, and the average of the 10 data points is taken as the measured value. The measurement is performed in an area that does not have metal grooves or urethane grooves.

[0148] Preferred materials for the head body include metals and fiber-reinforced plastics. Examples of the metals include titanium alloys, pure titanium, stainless steel, aluminum alloys, maraging steel, and soft iron. Examples of the fiber-reinforced plastics include carbon fiber-reinforced plastics. The head body may have a metal portion and a fiber-reinforced plastic portion. Examples of the materials for the metal face portion include titanium alloys, pure titanium, stainless steel, aluminum alloys, maraging steel, and soft iron.

[0149] Preferable materials for the metal face portion include titanium alloys, pure titanium, stainless steel, aluminum alloys, maraging steel and soft iron. EXAMPLES

[0150] [Example 1] The same head as the head 300 of the third embodiment was produced. The face member 300b was produced by forging. The back member 300c was produced by lost wax precision casting. The face member 300b and the back member 300c were joined by welding to obtain the head main body 300a. The material of the face member 300b was Super-TIX 51AF, and the material of the back member 300c was Ti-811Plus. The outer surface of the metal face part M3 of the face member 300b was subjected to surface processing by laser to increase the surface roughness. A urethane layer part U3 was molded separately from the head main body 300a. The urethane layer part U3 was produced by injection molding using thermoplastic polyurethane. As the thermoplastic polyurethane, which is the material of the urethane layer part U3, MDI-based polyurethane (trade name "Elastollan 1185A50" manufactured by BASF) was used. This urethane layer part U3 was bonded to the face member 300b. The adhesive used was "Chemlock 210" manufactured by Lord Japan Co., Ltd. The edge 330 of the urethane layer U3 was fitted into the groove 328 and adhered to the groove 328. In this manner, the golf club head of Example 1 was obtained. A shaft and a grip were combined with this head to obtain the golf club (length 45.5 inches) according to Example 1.

[0151] [Examples 2 to 10] Golf club heads and golf clubs of Examples 2 to 10 were obtained with the same specifications as Example 1, except for those shown in Tables 1 and 2 below. However, in Example 5, a metal groove shown in FIG. 26(a) was added. In Example 5, the width of the metal groove was 0.15 mm, and the depth of the metal groove was 0.15 mm. In Example 6, the embodiment shown in FIG. 27(a) was added. That is, Example 6 had a metal groove, an inner convex portion, and a urethane groove. The widths of the metal groove and the inner convex portion were 0.15 mm, and the depth of the metal groove and the height of the inner convex portion were 0.15 mm.

[0152] [Comparative Examples 1 to 4] Other than the specifications shown in Tables 1 and 2 below, golf club heads and golf clubs of Comparative Examples 1 to 4 were obtained in the same manner as Example 1. In Comparative Example 4, in which the thickness t is 0 mm, no urethane layer was provided, and the outer surface of the metal face was used as the striking surface. The roughness of the striking surface of Comparative Example 4 was the normal roughness adopted for a metallic striking surface.

[0153] The evaluation method is as follows.

[0154] [Arithmetic mean roughness Ra, maximum height Rz and developed area ratio Sdr] The arithmetic mean roughness Ra, maximum height Rz and developed area ratio Sdr of the outer surface of the metal face portion were measured by the above-mentioned method. These measured values ​​are shown in Tables 1 and 2 below.

[0155] [Thickness of urethane layer t] The thickness t of the urethane layer in the striking surface area was measured and is shown in Tables 1 and 2 below.

[0156] [Feeling of bite] Ten golfers with a handicap of 10 or less and a driver head speed of 45-50 m / s hit the ball with each club and rated the feeling of bite on a 5-point scale from 1 to 5. The higher the score, the higher the evaluation. The golf ball used was "SRIXON Z-STAR XV" manufactured by Sumitomo Rubber Industries. The average scores of the 10 golfers are shown in the "Feel of Biting" column in Tables 1 and 2 below.

[0157] [Flight distance] The 10 golfers hit five balls with each club, and the distances were measured. The total distance, including the run, was measured. The balls used were "SRIXON Z-STAR XV" manufactured by Sumitomo Rubber Industries. The average distances of all shots are shown in Tables 1 and 2 below.

[0158] [COR] COR was measured for the face center Fc. COR stands for Coefficient of Restitution. COR was measured based on "Interim Procedure for Measuring the Coefficient of Restitution of an Iron Clubhead Relative to a Baseline Plate Revision 1.3 January 1, 2006" prescribed by the USGA (United States Golf Association). The measured values ​​are shown in Tables 1 and 2 below.

[0159] [Table 1]

[0160] [Table 2]

[0161] After the above evaluation was completed, the state of the urethane layer was checked for all Examples and Comparative Examples, and it was found that a portion of the urethane layer had peeled off from the metal face portion in Comparative Examples 1 to 3. On the other hand, in Examples 1 to 10, no such peeling occurred, and the adhesion between the urethane layer and the metal face portion was maintained.

[0162] As shown in Tables 1 and 2, the Examples were rated higher than the Comparative Examples.

[0163] The following supplementary notes are part of the invention included in this invention. [Appendix 1] A golf club head having a face portion that forms a striking surface, The face portion has a metal face portion formed of metal and a urethane layer portion provided on the outer side of the metal face portion and formed of polyurethane, A golf club head, wherein in the portion covered with the urethane layer, the line roughness of the outer surface of the metal face portion is greater than 4.5 μm in terms of arithmetic mean roughness Ra, or greater than 25 μm in terms of maximum height Rz. [Appendix 2] 2. The golf club head according to claim 1, wherein the developed area ratio Sdr of the outer surface of the metal face portion in the portion covered with the urethane layer is 0.12 or more. [Appendix 3] 3. The golf club head according to claim 1, wherein the urethane layer has a thickness of 0.3 mm or more and 0.8 mm or less in the striking surface area. [Appendix 4] 4. The golf club head according to claim 1, wherein the outer surface of the metal face portion further has at least one groove, referred to as a metal groove, in the portion covered with the urethane layer portion. [Appendix 5] The outer surface of the urethane layer further includes at least one groove, referred to as a urethane groove; 5. The golf club head according to claim 4, wherein the urethane groove is provided at a position that does not overlap the metal groove. [Appendix 6] 6. The golf club head according to claim 4, wherein the inner surface of the urethane layer further has an inner surface protrusion that is recessed into the metal groove. [Appendix 7] A plurality of said metal grooves are provided; 7. The golf club head according to claim 4, wherein the plurality of metal grooves include metal grooves having different groove depths. [Appendix 8] the golf club head has a head body including the metal face portion and the urethane layer portion, When a plane tangent to the striking surface at the face center is defined as a reference plane, and a point of contact between a straight line that forms a 45-degree angle with this reference plane and the outer surface of the head is determined in a vertical section, and the set of these points of contact is defined as a 45-degree boundary line, The urethane layer portion extends to the back side of the 45-degree boundary line, 8. The golf club head according to claim 1, wherein the head body has an edge fixing portion that fixes an edge of the urethane layer on the back side of the 45-degree boundary line. [Appendix 9] 9. The golf club head according to claim 8, wherein the edge fixing portion is a groove, and the edge portion of the urethane layer is fitted into the groove. [Explanation of symbols]

[0164] 100, 200, 300, 400, 500, 600, 700, 800...Golf club heads 100a, 200a, 300a, 400a, 500a, 600a, 700a, 800a... Head body 102, 202, 302...Face part 102a, 202a, 302a... striking surface 102b, 202b, 302b... Face inner surface 104, 204, 304... Crown part 106, 206, 306... Sole part 108, 208, 308...Hosel part 120, 220, 320...Outer surface of metal face 124, 224, 324...Inner surface of urethane layer 126, 226, 326...Outer surface of urethane layer 130: Recess in which urethane layer is disposed 232...Edge of urethane layer 234 Edge fixing part 328...Groove 330... Edge of urethane layer 334 Edge fixing part 750···Inner convex part s4, s5, s6, s7, s8...metal groove g7···Urethane groove k1: Contour line of urethane layer k2, k3: Boundary between the urethane layer and the head body Fc···Face Center U1, U2, U3... Urethane layer M1, M2, M3...Metal face part

Claims

1. A golf club head having a face portion that forms a striking surface, The face portion has a metal face portion formed of metal and a urethane layer portion provided on the outer side of the metal face portion and formed of polyurethane, In the portion covered with the urethane layer, the line roughness of the outer surface of the metal face portion is greater than 4.5 μm in arithmetic mean roughness Ra, or greater than 25 μm in maximum height Rz.

2. 2. The golf club head according to claim 1, wherein a developed area ratio Sdr of the outer surface of said metal face portion in the portion covered with said urethane layer portion is 0.12 or more.

3. 3. The golf club head according to claim 1, wherein the thickness of the urethane layer in the striking surface area is 0.3 mm or more and 0.8 mm or less.

4. 3. The golf club head according to claim 1, wherein the outer surface of the metal face portion in the portion covered with the urethane layer further has at least one groove called a metal groove.

5. The outer surface of the urethane layer further includes at least one groove, referred to as a urethane groove; 5. The golf club head according to claim 4, wherein the urethane groove is provided at a position that does not overlap the metal groove.

6. 5. The golf club head according to claim 4, wherein the inner surface of the urethane layer further includes an inner surface protrusion extending into the metal groove.

7. A plurality of said metal grooves are provided; 5. The golf club head according to claim 4, wherein the plurality of metal grooves include metal grooves having different groove depths.

8. the golf club head has a head body including the metal face portion and the urethane layer portion, A plane that is tangent to the striking surface at the face center is defined as a reference plane, and a point of contact between a straight line that is at a 45-degree angle to the reference plane and the outer surface of the head is determined in a vertical section. The set of these points of contact is defined as a 45-degree boundary line. The urethane layer portion extends to the back side of the 45-degree boundary line, 3. The golf club head according to claim 1, wherein the head body has an edge fixing portion for fixing an edge of the urethane layer on the back side of the 45-degree boundary line.

9. 9. The golf club head according to claim 8, wherein the edge fixing portion is a groove, and the edge portion of the urethane layer is recessed into the groove.

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