Golf ball

Abstract: Disclosed is a coated golf ball comprising a golf ball having an ionomer resin cover and a paint layer thereon, wherein the ionomer resin cover contains substantially no fluorescent brightener, the Wcie reading which indicates the whitness after coating of the paint is within the range of from 110 to 125, the Tw reading which indicates greenishness is within the range of from 4 to 6.5, and the Wcie (Cw) and Tw (C T ) reading of the cover and the Wcie (Pw) and Tw (P T ) reading obtained after coating of the paint have the following relationship: 4 ≦ Pw - Cw ≦ 12 0 ≦ C T - P T ≦ 1.22.

Description: The present invention relates to a coated golf ball. More particularly, it relates to a coated golf ball which does not show a remarkable color change even when the surface paint layer has a defect such as a scratch or peeling. Regarding a golf ball, the ball surface is scratched by a grooved clubface when it is hit by a golf club, particularly a short iron, whereby the paint layer is sometimes peeled off. Heretofore, an attempt has been made to put the same color tone in both the cover and the paint layer so that the golf ball does not show a remarkable color change. In the combination of a cover and a paint layer both of which contain a brightener, it is possible to prevent a remarkable color change when the paint layer is peeled off, by putting the same color both in the cover and the paint. However, when a brightener is contained in the cover of the golf balls, the degree of discoloration due to ultraviolet rays becomes large and is not preferred. Therefore, a golf ball in which the brightener is not formulated into the cover but is formulated into the paint layer has become popular. However, even by putting the same color in both the cover and the paint layer, the golf balls show scratches in comparison with golf balls in which the brightener is formulated in both cover and paint. We have now developed a coated golf ball which does not show a remarkable color change due to a defect, such as a scratch in or peeling of the paint layer, even though the cover of the golf ball does not contain a fluorescent brightener. According to the present invention, there is provided a coated golf ball comprising a golf ball having an ionomer resin cover and a paint layer thereon, wherein the ionomer resin cover contains substantially no fluorescent brightener, the Wcie reading which indicates the whitness after coating of the paint is within the range of from 110 to 125, the Tw reading which indicates greenishness is within the range of from 4 to 6.5, and the Wcie (Cw) and Tw (C T ) reading of the cover and the Wcie (Pw) and Tw (P T ) reading obtained after coating of the paint have the following relationship: 4 ≦ Pw - Cw ≦ 12 0 ≦ C T - P T ≦ 1.22. The golf ball of the present invention has an ionomer resin cover around a core. The ionomer resin may be anyone which is commercially available, those which are available from Du Pont de Nemours & Co. under the trade name of SURLYN being preferred. If necessary, pigments (e.g. titanium dioxide, barium sulfate, etc.) may be contained therein in an amount of from 0.5 to 10% by weight, based on the weight of the ionomer resin of the cover. Furthermore, the resin may also contain polyester, nylon, or an ionomer-polyester terpolymer. In the present invention, the ionomer resin cover contains substantially no fluorecent brightener. The description "...contains substantially no fluorescent brightener" means that the cover may contain a fluorescent brightener in such a small amount that the function thereof is insufficiently accomplished. The golf ball of the present invention is coated with an enamel containing 0 to 12% by weight of a pigment or a clear paint. The enamel or clear paint may be of the urethane type, acrylic type or epoxy type. The enamel or clear paint can be either solvent-borne or water-borne. The color matching of both the cover and the paint is conducted, using titanium dioxide in combination with suitable organic or inorganic pigments. As the main organic pigment, for example there can be used an insoluble azo pigment, condensed azo pigment, phthalocyanine pigment, quinacridone pigment or dioxane pigment. As the inorganic pigment, for example, there can be used a silicate, ferrocyanide or phosphate pigment. They may be appropriately combined. The pigment may preferably be contained in an amount of from 0.001 to 5.0% by weight, based on the weight of the resin. The paint generally contains a fluorescent brightener. As the brightener, UVITEX OB (manufactured by Ciba-Geigy Ltd.) or WHITEFLOW (manufactured by Sumitomo Chemical Industries Co.) may be used in an amount of from 0.01 to 1.0% by weight, based on the weight of the resin. In the present invention, the Wcie reading which indicates whiteness after coating of the paint is within the range of from 110 to 125, preferably from 112 to 123, the Tw reading which indicates greenishness is within the range of from 4 to 6.5, preferably from 4.2 to 6.3, and the Wcie (Cw) and Tw (C T ) reading of the cover and the Wcie (Pw) and Tw (P T ) reading after coating of the paint have the following relationship: 4 ≦ Pw - Cw ≦ 12 0 ≦ C T - P T ≦ 1.2 The Wcie and Tw readings are calculated from the following equations: Wcie = Y + 800 (Xo - x) + 1700 (Yo - y) Tw = 1000 (Xo - x) - 650(Yo - y) wherein Xo and Yo are the chromaticity co-ordinates of perfect diffuse surface of D 65 illumination, and Xo is 0.3127 and Yo is 0.3291, based on the whiteness of CIE ISO according to IS0 105-J01: 1987 (E). When these values are not in the above range, the golf ball shows a remarkable color change when it is scratched or the paint peels off. That is, it is possible to prevent a defect from showing by enlarging the Wcie as whiteness of the paint layer in comparison with that of the cover layer within a suitable range and by enlarging the greenishness of the cover layer in comparison with that of the paint layer within a suitable range. It is preferred that the b* reading, which indicates a yelloweish-bluish in color difference on the coated golf ball is -5.0 to -10.0, preferably -6.0 to -9.0. When the b* reading is larger than -5.0, the golf ball becomes yellowish. Further, when the b* reading is smaller than -10.0, the golf ball becomes too bluish and is not of suitable appearance for a golf ball. The L*a*b* color difference is calculated as described in the following equations, using tristimulus values according to JIS Z8701 or JIS Z8728. L* = 116(Y/Yn) 1/3 - 16 a* = 500[(X/Xn) 1/3 - (Y/Yn) 1/3 ] b* = 200[(Y/Yn) 1/3 - (Z/Zn) 1/3 ] wherein Xn, Yn and Zn are tristimulus values in XYZ system of perfect diffuse reflection surface. According to the above equations, "L*" reading represents lightness and "a*" and "b*" readings represent chromaticity. Particularly, the "a*" reading represents a redgreen direction and the "b*" reading represents a yellow-blue direction. Further, when the "L*" reading becomes larger, the lightness becomes larger. When the "a*" reading becomes larger, the color becomes red. When the "b*" reading becomes larger, the color becomes yellow. In the present invention, the L*a*b* color difference is measured, using a colorimeter (commercially available from Minolta Co. as CR-221). By changing conditions such as the type and amount of pigment as well the type of cover and paint, control of the color tone can be achieved. According to the present invention, by combining the color tone of the cover with that obtained after coating of the paint within a suitable range, a golf ball having a preferred white appearance and small weather discoloration, which does not show a remarkable color change due to defects after scratching, can be obtained. Example The following Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof. Examples 1 to 6 and Comparative Examples 1 to 6 A two piece golf ball wherein an ionomer resin [SURLYN/Ti0 2 = 98:2 (weight ratio)] was used as a cover was coated with a paint shown in Table 1 in the form of coating shown in Table 1. Appearance, discoloration after weathering and ease of showing after scratching of the resulting golf ball were evaluated. The results are shown in Table 1. Test method (1) Measurement of color tone By using a colorimeter CR221 manufactured by Minolta Co. (2° visual field, 3 mm, light source D 65 ), Yxy measurement was conducted and color tone was calculated from the following equations [whiteness of CIE ISO]: Wcie = Y+800(Xo - x) + 1700(Yo - y) Tw = 1000(Xo - x) - 650(Yo -y) wherein Xo and Yo are chromaticity co-ordinates of perfect diffuse surface of D 65 lighting, and Xo is 0.3127 and Yo is 0.3291. (2) Discoloration after weathering A sample was treated by a Sunshine Weather-o-meter for 120 hours and ΔL*, Δa*, Δb* and ΔE* were determined from L*, a* and b* obtained before and after treatment by a colorimeter. Further, visual observation was conducted according to the following criteria (n = 12). A: Degree of discoloration is extremely small (good). B: Degree of discoloration is large (inferior). (3) Ease of showing after scratching A professional golfer was allowed to hit at a club-head speed of about 30 m/second with a golf club of sand wedge and appearance was evaluated by the following criteria (n = 12). A: The golf ball hardly shows scratch. B: The golf ball remarkably shows scratch.

Claims: A coated golf ball comprising a golf ball having an ionomer resin cover and a paint layer thereon, wherein the ionomer resin cover contains substantially no fluorescent brightener, the Wcie reading which indicates the whiteness after coating of the paint is within the range of from 110 to 125, the Tw reading which indicates greenishness is within the range of from 4 to 6.5, and the Wcie (Cw) and Tw (C T ) reading of the cover and the Wcie (Pw) and Tw (P T ) reading obtained after coating of the paint have the following relationships: 4 ≦ Pw - Cw ≦ 12 0 ≦ C T - P T ≦ 1.22. A coated golf ball as claimed in claim 1 wherein the b* reading in the L*a*b* color difference is within the range of from -5.0 to -10.0. A coated golf ball as claimed in claim 1 or claim 2 wherein the Wcie reading is within the range of from 112 to 123. A coated golf ball such as claimed in any one of the preceding claims wherein the Tw reading is within the range of from 4.2 to 6.3.

Inventors: EBISUNO TADAHIRO, HORIUCHI KUNIYASU, MORIYAMA KEIJI, EBISUNO, TADAHIRO, HORIUCHI, KUNIYASU, MORIYAMA, KEIJI
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES, CO. LTD
Application year: 1993
Main classification: A63B37
IPC codes: A63B37, A63B45