Fluorescent Marking

Abstract

Container caps or containers having a varnish outer coating, or other resinous outer surface, are coded by marking indicia thereon with a fluorescent ink made of a fluorescent brightening agent in an organic solvent but having no resinous vehicle. The solvent softens the varnish and the fluorescent brightening agent penetrates into the varnish layer to remain therein after the solvent is dried off and is brought to view when desired by exposure to ultraviolet light.

Description

SUMMARY OF THE INVENTION

As is well known, many consumer products, and particularly food products bear dates or other specific information on their containers so that the age, or batch of the product may be ascertained. For some products, such as bottled beverages, normally visible identification markings are inconvenient because bottle caps bearing brand and/or flavor indicia have very little available space for additional identification markings. In addition, the bottle caps are usually printed in advance of bottling and the application of visible identification indicia thereto would obliterate the printing.

To deal with this problem, it has been proposed to mark the bottle caps with the desired indicia using a fluorescent ink. U.S. Pat. application Ser. No. 776,192 , filed by James G. Smith on Nov. 15, 1968 (now abandoned), discloses a coded bottle cap which has a fluorescent ink applied to its outer surface leaving a resinous, normally invisible deposit of the fluorescent material on said outer surface as the desired indicia, which becomes visible when exposed to ultraviolet light.

In some instances, bottle caps are subject to surface abrasion in normal use. For example, it is common in the beverage bottling industries to place filled and capped bottles upright into subdivided cases and to stack the filled cases so that each case above the lowest rests directly on the bottle caps of the next case therebelow. In such instances, it has been found that fluorescent markings applied as a separate layer in a resinous matrix are sometimes abraded off and obliterated to the point of illegibility.

In accordance with one aspect of the present invention, bottle caps, or other closure members for open containers, having an adherent, resinous coating layer on an outer surface are marked in limited areas on said coating layer with a fluorescent ink composition consisting essentially of a fluorescent brightening agent in a volatile organic solvent capable of softening said adherent coating layer in the marked areas while said areas are wet with said solvent. The ink is free of resinous binders.

THE DRAWINGS

FIG. 1 is a plan view of a bottle cap showing the coded indicia on exposure to ultraviolet light to obtain visual presentation thereof and wherein the normally printed material is shown in phantom;

FIG. 2 shows the bottle cap in ordinary light with the normally printed visible material thereon and wherein the normally invisible transparent indicia are indicated in phantom;

FIG. 3 is a sectional view, greatly enlarged showing a small segment of the crown of the bottle cap immediately after application of the fluorescent ink thereto;

FIG. 4 shows a still greater enlargement of a portion of the segment of FIG. 3 after penetration of the fluorescent ink into the outer varnish layer of the cap and the evaporation of surface solvent therefrom; and pg,4

FIG. 5 shows the same segment as FIG. 4 after the cap has reached its final stable condition and the subsurface ink solvent has evaporated.

Referring now to the drawings, there is shown one embodiment incorporating the present invention. FIGS. 1 and 2 are plan views of a crown bottle cap 10 having a generally flat top surface 12 and having a depending skirt portion with the standard serrations 14 around the periphery of the skirt.

The top surface 12 of the bottle cap 10 is shown with a design 16 imprinted thereon. Such printed material may take the form of a legend identifying the manufacturer of the product, or identifying the product, or in the case of soft drinks, the flavor of the product, or maybe some combination of all three.

The normally invisible indicia 18 of the present invention are imprinted over the top of the design 16 which is present on the top 12 of the bottle cap 10 and may very well be repetitive in nature, such as shown in FIG. 1. Typical of the purpose of such coded indicia would be to identify the date on which the product was inserted within the bottle to which the cap 10 is applied. Thus, in the embodiment shown in FIG. 1, the contents would have been packaged Jan. 23 , 1964 . It is quite clear, however, that any combination of coded indicia can be utilized and the present invention is not limited to the particular arrangement shown in the drawings.

The coded indicia, as explained more fully hereinbelow, are formed from a fluorescent brightening agent embedded in an outer adherent coating, such as a varnish or other resinous coating. The brightening agent is normally invisible, but is rendered visible when subjected to an ultraviolet light.

Typically, such a cap is a multilayered construction in which the base, or substrate 20, is formed, typically, either from an electrolytic tin plate or from aluminum. Depending upon the design and the use to which the cap is being put, an organic sizing 22 is applied to the surface of the substrate 20. If desired, an organic, pigmented coating 24 may then be applied over the sizing.

Following this, the decorative or functional ink pattern 16 is applied over the surface of the pigmented coating 24 in one or more colors. A final protective clear, or slightly pigmented finishing varnish 26 is applied over the printing to provide abrasion and corrosion resistance for the finished product. A typical varnish is an epoxy ester of a drying oil such as a dehydrated castor oil.

At this stage the bottle cap manufacture is completed and the caps are sent to the bottler who uses them to seal filled beverage bottles and generally applies the normally invisible coded indicia 18 to the caps after filling and capping the bottles.

The indicia are applied by marking the cap with a fluorescent ink free of resinous binders and consisting essentially of a fluorescent brightening agent in a volatile organic solvent. The markings may be applied by any suitable method or apparatus, a suitable method and apparatus being described in U.S. Pat. application Ser. No. 776,114 , filed Nov. 15 , 1968 , by Sheldon L. Wilde.

Immediately after the application of the fluorescent ink markings, the liquid ink composition is on the surface of the varnish outer layer in localized marked areas, as indicated by 18a in FIG. 3.

Very shortly thereafter, the ink solution penetrates into and somewhat softens the varnish layer in the marked areas, as illustrated at 18b in FIG. 4, and whatever surface solvent has not penetrated is volatilized off.

Finally, and very shortly after the stage of FIG. 4, the solvent which penetrated into the varnish layer is volatilized off, leaving behind the fluorescent brightening agent in the formerly softened (and now rehardened) areas of marking, as shown by 18c .

In order to provide optimum results, the volatility of the ink solvent should be controlled. If the solvent is too volatile, it will evaporate off the surface of the varnish layer before it has had an opportunity to soften and penetrate it. In that case, the fluorescent brightening agent will be deposited on the surface of the varnish layer in the form of a nonadherent coating, and will not provide the desired permanency of the fluorescent markings.

On the other hand, if the ink solvent is too low in volatility, the varnish will lift and the printing will smear when the bottles are handled. For optimum results, the solvent should be one which has a drying time from about 1.7 to about 3.5 times as long as that of n-butyl acetate. Suitable solvents include alcohols, esters, ketones and aliphatic hydrocarbons. Aromatic hydrocarbons and chlorinated hydrocarbons may also be used, provided that the print wheel of the marking device is made of a material resistant to these solvents. Specific solvents of these classes which may evaporate too quickly or too slowly may be blended with other solvents to bring their drying times (from a fully exposed surface under ambient conditions) within the optimum range.

A particularly suitable solvent system is one containing from about 50 to 75 weight percent of denatured ethyl alcohol and from about 25 to 50 weight percent of methyl isobutyl ketone, and most preferably 59.75 weight percent of the alcohol and 39.75 weight percent of the ketone.

Any of the known fluorescent brightening agents which are soluble in organic solvents may be used as the fluorescent brightening agent in this invention, the choice being made on the basis of color desired (when fluoresced), cost, strength, and other properties.

Suitable fluorescent brightening agents are disclosed in the "Colour Index," Volume 2--Second Edition, 1956 and 1963 Supplement, published by The Society of Dyers And Colourists, Dean House, Picadilly, Bradford, Yorkshire, England. Suitable fluorescent brightening agents are those identified as Calcofluor RWP (described in the "Colour Index" as Fluorescent Brightening Agent 61) which provides a bluish violet fluorescence, Hiltamine Arctic White SOL (described in the "Colour Index" as Fluorescent Brightening Agent 68, and also Fluorescent Brightening Agents 57, 69, 73, 74fluoresces greenish yellow), 75 (fluoresces greenish yellow), 76 (fluoresces greenish blue), 77 (fluoresces reddish blue), 78, 91 (bright reddish fluorescence), 128 (bluish violet fluorescence), 130 (violet fluorescence), and 132 (blue fluorescence).

Generally, the amount of fluorescent brightening agent in the fluorescent ink will be between about one-eighth weight percent and about 5 weight percent with amounts between about one-fourth and one-half weight percent being preferred.

While the invention has been described with respect to a specific embodiment, it is to be understood that modifications may be employed, as will be understood by those skilled in the art, without departing from the invention defined in the claims.

For example, the invention is applicable to the fluorescent marking of articles other than the bottle caps specifically disclosed. Container caps, generally, including caps for wide mouth jars, may be marked in accordance with this invention provided that they have an outer resinous surface which is susceptible to solvent penetration. Metallic container caps usually have an outer resinous coating layer which is at least partially solvent softenable and in resinous container caps the outer surface itself is receptive to solvent penetration. Even thermoset resinous materials such as phenol-formaldehyde and urea-formaldehyde resins are sufficiently surface-softenable by solvents to permit marking by the ink of this invention.

The invention is also suitable for the marking of container bodies, rather than caps, and in fact, for the marking of any article having an outer surface which is softenable by an organic solvent so that the ink may penetrate it, whether said outer surface is a coating layer or an integral part of the material of construction of the article.

The invention finds its greatest applicability in the marking of relatively small surfaces such as bottle caps because such surfaces, when they already bear labelling indicia, have very little space for additional visible marking indicia. However, even on relatively large surfaces, the marking with a visible ink is disadvantageous on a rapidly moving production line because roller printing is unsightly and spot printing raises difficult mechanical problems in securing registry between the printing surface and the rapidly moving bottle caps.

Claims

We claim:

1. A coded article comprising a body having a resinous outer surface and a normally invisible fluorescent dye incorporated within said surface in certain selected areas to comprise indicia visible in response to ultraviolet light.

2. The article of claim 1 wherein said outer surface comprises an adherent coating layer.

3. A coded container cap comprising a rigid body adapted to be attached to an open container as a closure therefor, said cap having on an outer surface an adherent, resinous coating layer and a normally invisible fluorescent dye incorporated within said layer in certain selected areas to comprise indicia visible in response to ultraviolet light.

4. The coded cap of claim 3 wherein said container is a glass beverage container and said cap is a crown closure therefor.

5. The coded cap of claim 3 wherein said adherent coating on said outer surface overlays an intermediate pigmented coating containing normally visible indicia.

6. The coded cap of claim 3 wherein said adherent coating on said outer surface comprises a finishing varnish.