PHOTOCHROMISM GOLF BALL TECHNICAL FIELD The present invention relates, in general, to a photochromism golf ball which changes from white to another bright color when exposed to direct sunlight and, more particularly, to a photochromism golf ball, in which a photochromic compound is evenly dispersed in a cover layer or a transparent coating layer, so as to enable the golf ball, which is white when it is shielded from direct sunlight, to change to another bright color when it is directly exposed to sunlight.

BACKGROUND ART Golf requires a player to strike a small ball with various clubs from a series of starting points (teeing grounds) into a series of holes on a course. Among players, a player who sinks his ball in a hole the fewest strokes wins. Although golfs place of origin is uncertain, it is believed that Scotland has the longest history.

The standard course consists of 18 consecutively numbered"holes" (the playing areas leading to the cups). The cup measures 4.25 inches in diameter and 4.0 inches or longer in depth and is set into a smooth surface of closely cropped grass, called a green. While playing on a golf course, on average the players walk about 6-7 km over about 4-5 hours while friendly talking with each other.

As golf has been recently popularized as a leisure sport, there is a highly increased demand for golf products such as golf balls, golf clubs and like. The present invention is concerned with golf balls, especially photochromism golf balls which change in color when exposed to sunlight. There have been disclosed fluorescent golf balls or photochromism golf balls whose colors are changed according to UV light, but not yet according to sunlight.

Most golf balls are white. Occasionally, colored golf balls are used in the winter. Various pigments, such as organic, inorganic, phosphorescent, and fluorescent pigments, are used to dye golf balls with various colors. However,

other colors than red-like colors, such as red and orange, are difficult to find in golf balls used in the winter.

One basic principle underlying nearly all the rules is that players must play only their own ball, and not touch it (except to hit it with a club) until play is completed on the hole. Usually, four players play together in a golf game. When all the accompanying players use white balls of the same brand, confusion may arise about which golf ball is whose. In this case, each of the players discriminates his own ball from other's with the numerals marked on the golf balls. However, if the numerals cannot be seen for various reasons, for example, they are screened by the ground, glasses, or other hindrances, the playing companions cannot discriminate the golf balls without moving the golf balls, which violates the rule. In fact, this case occasionally happens during golf.

Colored golf balls may be the solution to the problem. That is, if four playing companions use golf balls with four different colors, they can easily discriminate the golf balls and play the game without violating the rule. From this point of view, there is needed the use of colored golf balls. However, most golf players prefer white golf balls to other colored ones. Additionally, in order for four companions to play golf with golf balls of different colors, as many as 12 golf balls would be needed according to the golf ball package system in current use (three per color x four colors).

DISCLOSURE OF THE INVENTION The present invention is directed to a photochromism golf ball which changes to a bright new color when exposed to direct sunlight while remaining in its original color where sunlight is not illuminated such as in golf bags or pockets.

Specifically, the present invention is directed to a golf ball comprising a core 2, a cover, a cover 3 provided with a number of dimples thereon, enclosing the core 2, and a transparent coat 4 on the cover 3, wherein the cover 3 or the transparent coat 4 contains a photochromic compound.

In the photochromism golf ball of the present invention, a dye which displays a light, clear color under sunlight is uniformly dispersed over the cover or

the transparent paint. The golf ball of the present invention remains white in the absence of sunlight such as within pockets or golf bags while changing into a predetermined color when exposed to sunlight. The color change of the golf ball is reversible.

In the present invention, the photochromism golf ball can be prepared by the application of a photochromic compound whose color state changes with exposure or lack thereof to direct sunlight. The golf ball according to the present invention may have a one-piece structure or multi piece structure. For example, the golf ball of the present invention may be a 2-piece or a 3-piece ball, or a higher- multi piece ball. In such typical golf ball structures, the photochromic compound is contained in a cover layer for 2-piece golf balls, in an outer cover layer for 3-piece golf balls, or in a transparent coating paint for all kinds of pieces. For example, the photochromism golf ball of the present invention may be a 2-piece structure consisting of a core, a cover layer with dimples, and a transparent coat on the cover layer, where a photochromic compound is contained in the cover layer or the transparent coat. In this regard, the photochromic compound is homogeneously mixed with a synthetic resin for golf ball cover, and the mixture is molded into a cover layer for golf balls by injection. Alternatively, the photochromic compound may be homogeneously mixed with a transparent paint for coating the golf balls.

Any compound, if it can change its color according to direct sunlight, may be used in the present invention, but preferable are those exemplified by spiro (2H- 2, 3- (3H) naphtha (2, 1-b) (1, 4) oxazine)-1, 3-dihydro-1, 3, 3-trimethyl-6'- (l-piperidinyl) (represented by the general formula of C27H29N3O, sold in the trade name of"Photo Chromic Violet", CAS No. 114747-45-4) which turns violet when being exposed to direct sunlight, 1,3-dihydro-1, 3, 3-trimethyl-6'- (2, 3-dihydro-1H-indole-1- yl) spiro [2H-indole-2, 8'- [3H] naphtho [2, 1-b] [1, 4] oxazine (sold in the trade name of "Photochrome Blue", also called"Spironaphthoxazine") which turns blue when being exposed to direct sunlight, and 3,3-diphenyl-3H-naphtho (2, 1-b) pyran (represented by the general formula of C25HI8O, sold in the trade name of Photo Chromic Yellow, CAS No. 4222-20-2) which turns yellow when being exposed to direct sunlight. Additionally, photochromic compounds which appear red, pink or orange in the presence of direct sunlight may be used in the present invention.

As a result, although the photochromism golf ball of the present invention displays a white color or a shade of a white color when it is shielded from direct sunlight, the photochromism golf ball containing the compound of"Photo Chromic Violet"changes to violet from white, the photochromism golf ball containing the compound of"Photochrome Blue"changes to blue from white, and the photochromism golf ball containing the compound of"Photo Chromic Yellow" changes to yellow from white, when it is directly exposed to sunlight in the field.

The photochromism golf ball of the present invention has the same structure as conventional ones with the exception of a photochromic compound. For example, like a conventional 2-piece ball, the photochromism golf ball has a structure consisting of a core 2, a cover 3 which encloses the core 2 and has a number of dimples 5 thereon, and a transparent coat 4 over the cover 3.

The golf balls of the present invention can be manufactured by a conventional method. With reference to the accompanying drawing, the core 2 is made of a synthetic rubber of high resilience. Onto the core 2, the cover 3 is molded from an ionomer resin (e. g. , sold in the trade name of"Surlyn"from DuPont<BR> U. S. A. ) by a well-known technique, for example, injection or pressing. After being provided with dimples 5, the cover 3 is coated with a transparent paint by, for example, spraying. The core 2 may have a central cavity. As for a 3-piece golf ball, it has comprises an inner cover layer and an outer cover layer, instead of the cover 3.

In accordance with the present invention, a photochromic compound is contained in the cover 3 (the outer cover layer for a 3-piece golf ball) or in the transparent coat 4 on the cover 3. In this regard, together with additives such as dispersants, the photochromic compound is homogeneously mixed with an ionomer resin and the mixture is, for example, injection-molded at a uniform thickness on the core 2 to form the cover 3. As mentioned above, if the golf ball has a three-or more multi structure, the photochromic compound is preferably contained only in the outer cover layer. Depending on the photochromic compound, the color of the golf ball is determined when it is illuminated with direct sunlight.

Alternatively, the photochromic compound may be uniformly mixed with a typical transparent paint composition, such as polyurethane resin-based composition.

The mixture is then coated on the cover 3 by a conventional technique such as spraying.

In accordance with the present invention, the cover 3 or the transparent paint 4 comprises photochromic compound in the amount of 0.1 to 5 % by weight.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view showing the structure of a two-piece golf ball in accordance with an embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION Hereinafter, the present invention can be more understand in the following example.

EXAMPLE Preparation of Core Ball 2 A well-known conventional synthetic rubber composition suitable for the preparation of core balls was vulcanized at around 160 °C for 30 min in a typical mould to prepare a core ball for 2-piece golf ball, which measured 38. 4 mm in diameter.

Formation of Photochromism Cover 3 A typical cover resin composition was mixed with photochromic compounds and additives as shown in Table 1, below and the resulting mixtures were injected into covers 3 in a thickness of 2.3 mm onto the core ball. After the formation of dimples on the covers, a conventional transparent paint composition was coated on the covers.

TABLE 1 Examples Comparative Ex. 1 2 3 Cover Resin Composition 98.9 96 94 99 Photochromism 0. 1 3 5 Cods. l Additives2 1 1 1 1 Note.'Example 1 : Photo Chromic Violet Example 2: Photochrome Blue Example 3: Photo Chromic Yellow 2Additives : Ca lubricant, dispersant, antioxidant, etc.

Formation of Photochromism Transparent Coat 4 On the cover prepared with the composition of Comparative Example 1 of Table 1, compositions formulated with a typical urethane resin-based, transparent paint, photochromic compounds and additives as shown in Table 2, below, were sprayed to form photochromism transparent coats which were 0.2 mm thick.

TABLE 2 Examples Comparative Ex. Compositions 4 5 6 2 Transparent paint 97. 9 95 93 98 Photochromism 0. 1 3 5 Cpds.' Additive l2 l 1 1 Additive 23 1 1 1 Note.'Ex. 5: Photo Chromic Violet Ex. 6: Photochrome Blue Ex. 7: Photochromism Yellow 2 Curative 3 Dispersant Color Observation

The golf balls manufactured according to Examples 1 to 6 were observed to be white in color in rooms where direct sunlight was not directly illuminated or in the shade and to change in color as shown in Table 4, below, under the direct sunlight. Blockage of the direct illumination of the direct sunlight gradually turned the colors back to white. To determine the brightness and saturation of the colors, the golf balls were measured for color coordinates and luminance at the distance of 170 cm by use of a luminance meter (BM-7 manufactured by TOPCON. Japan) after being exposed for five min to direct sunlight. It was measured that the golf balls of Examples 3 were the strongest and the golf balls of Examples 4 were the palest in color.

TABLE 3 Golf Balls Color in room Under Sunlight Examples 1 & 4 White Violet Examples 2 & 5 White Blue Examples 3 & 6 White Yellow Strength Test 1. Method: the golf balls (Example 3 and Comparative Example 2) were repetitively jetted through a one-meter long pipe into a disk 10 cm in diameter (10° loft, groove formed as in iron club). The durability of the golf balls was expressed as a hit number until the golf balls were broken.

2. Result Golf Balls Hit No. Comparative Ex. 2 130 (general 2PC) Example 3 130 Note: measured with a durability tester 3. Analysis The golf ball containing a photochromic compound in the largest amount showed the same durability as in a conventional 2-piece ball.

On the surface of the golf ball which comprises a photochromic compound- dispersed cover or transparent coat, the color to be changed by direct sunlight can be expressed. For example, numerals or brands, which are usually printed on golf balls, can be expressed in the color to be disclosed. Alternatively, a colored solid or dotted line may be printed to express the color. According to these color identifications, the playing companions can avoid using the golf balls of the same color.

The photochromism golf balls according to the present can be packed in the number of three in a box, which are different in color from each other.

Accordingly, even when each of the golf players has only one or two boxes, the golf players can avoid playing with golf balls of the same color.

INDUSTRIAL APPICABILITY As described hereinbefore, the golf balls of the present invention may be manufactured to be white in color when in the shade, meeting the color preference of most golf players while being colored under direct sunlight. The colors disclosed under direct sunlight allow the players to recognize their own golf ball from a distance, with the accompanying benefit of not needing to ever touch the golf ball.

Additionally, the clear, bright colors under direct sunlight greatly decreases the number of lost golf balls of the present invention. Further, from the point of teeing up, the golf balls are changed in color, so that the players can play the game while enjoying the color change. Moreover, when golf players tee off, they can pay more attention to the golf balls because of the color change. Also, because the color of the golf balls is restored to its original white when the golf balls are placed in pockets, the golf balls of the present invention may give the opportunity for the golf players to make conversation with one another in regard to the color change.

On the surface of the golf ball which comprises a photochromic compound- dispersed cover or transparent coat, the color to be changed by direct sunlight can be expressed. For example, numerals or brands, which are usually printed on golf balls, can be expressed in the color to be disclosed. Alternatively, a colored solid or dotted line may be printed to express the color. According to these color identifications, the playing companions can avoid using the golf balls of the same color.