Enhanced color change interlocking closure strip

#The instant invention relates to interlocking colored closure strips having improved color change characteristics when viewed in their occluded form. These interlocking colored closure strips may be employed as fasteners in traditional fastener areas and find particular use as closures for storage containers, e.g., plastic bags.

#The use of closure fastening devices for the closure of containers, including plastic bag bodies, is generally known. Furthermore, the manufacture of closure fastening devices made of plastic materials is generally known to those skilled in the art relating to closure fastening devices as demonstrated by the numerous patents in this area.

#A particularly well-known use for closure fastening devices is in connection with a flexible container, e.g., bag bodies. The closure fastening device and the associated container may be formed from thermoplastic materials, and the closure fastening device and sidewalls of the container can be integrally formed by extrusion as a single piece, or may be formed as separate pieces and then connected by heat sealing or other suitable fastening means.

#FIG. 1 is a cross-sectional view of a prior art closure device.

#FIG. 2 is a cross-sectional view of a prior art closure device.

#FIG. 3 is a cross-sectional view of a prior art closure device.

#The instant invention provides interlocking closure devices having improved color change characteristics when viewed in their non-occluded position in comparison to their occluded position. The interlocking closure devices include two closure elements arranged to be interlocked over a predetermined length, each of the closure elements having different colors for establishing visually the completeness of the occlusion of the closure elements by providing a combined color different from the closure elements that are occluded. It has been discovered that the perceivable color change is related to the width of the closure elements, the presence of guide members on the closure element(s) and combinations of these factors. The occluded color change is enhanced, i.e., is more perceivable to the viewer, by introducing a color change enhancement member in the internal channel of a translucent closure element whereby the color change of the closure elements before as compared after occlusion is improved when compared with the color change of a substantially similar closure device but as determined without the color change enhancement member. The terms "male" and "female" closure elements are generally understood in the art as closure elements wherein the element that interlocks into the other closure element and having outwardly projecting hooks is referred to as the "male closure element" and the outer element is referred to as the "female closure element" and has inwardly projecting hooks. These terms have been employed to define closure elements without any guide members. The characteristics of this color change enhancement member and its relationship to the male and female closure elements is discussed hereinafter.

#The color change enhancement member may be provided to enhance the color change in a wide variety of interlocking closure fastening devices when such are used as color change closures. A "color change closure" comprises a combination of a male closure element of one color, a female closure element of a different color which upon occlusion provide a third and perceivably different color. The interlocking closure fastening device may be as shown in reissue U.S. Pat. Nos. 28,969, 4,212,337; or as shown in FIG. 5 of U.S. Pat. No. 3,054,434, copending U.S. Ser. No. 774,400, filed Sept. 11, 1985 and U.S. Ser. No. 774,997, filed Sept. 11, 1985 each of the aforementioned items incorporated herein by reference. The interlocking closure fastening devices disclosed in copending U.S. Ser. Nos. 509,388, filed June 30, 1983 and 690,207, filed Jan. 10, 1985, incorporated herein by reference may also be employed in the instant invention as the closure to which the color change enhancement member is introduced when such closure devices are employed as a color change closure device. In addition, guide members may be provided adjacent each of the aforementioned closures of said patents.

#The nature of the relationship of the color change enhancement member to the interlocking closure fastening device of which it is an integral part is subject to several variables. These variables include the particular optical properties of the closure elements without a color change enhancement member, the geometry of the color change enhancement member and its light directing properties, the individual and combined optical properties of the aforementioned closure elements and the physical characteristics of the material of construction, e.g., selected plastic, coloration pigments, etc., of the male and female elements of the interlocking closure fastening device. The particular relationship between the color change characteristics of a color change closure is related to the geometry of the color change enhancement member. Such geometrical considerations include the height, width, shape (face angles) and the relative position of the color change enhancement member within the closure element. In addition, the selected geometry of the color change enhancement member is related to the light scattering characteristics of the closure element independent of the color change enhancement member and also when considered in combination with the color change enhancement member. The light scattering characteristics of the closure element are influenced by the depth of the channel of the closure element, the presence of guide members, the width of the closure element and the like. In addition, characteristics of the plastic material of construction, including pigments, TiO.sub.2 concentration, and the like may affect the color change characteristics of a color change closure.