Abstract:
Product and process for heat transfer labeling employing a contoured thermoplastic and resinous release layer which is desirably imprinted on a carrier and superimposed with a transfer layer containing a design print.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the labeling of objects by the use of heat to transfer design prints from a carrier to the objects being labeled. 
     In heat transfer labeling, a design print that is affixed to a carrier by a release layer is brought into contact with an object to be labeled. When heat is applied to the carrier the release layer becomes molten and permits the design print to become adhered to the object. 
     In the typical heat transfer label, as exemplified by U.S. Pat. No. 3,616,015, which issued Oct. 26, 1971, the release layer is a coating of wax on the carrier and the design print is in a transfer layer that is printed on the wax coating. With such a label, the application of heat during the transfer process causes a film of wax to be deposited over the entire region where the carrier is in contact with the object being labeled. The deposited film is of random configuration and is frequently much larger than the design print. 
     Although the wax film is transparent and generally not noticeable by casual observation, under certain lighting conditions the film is viewable and can present an objectionable appearance. The resulting film can be regarded as an expanded, irregular &#34;halo&#34; that surrounds the design print. Not only can the irregular halo present an objectionable appearance, it represents a wastage of material. Moreover, because of the tendency of the wax to penetrate the carrier material used in ordinary heat transfer labeling, a substantial amount of wax material is needed to form the transfer coating. 
     Accordingly it is an object of the invention to expedite and facilitate the heat transfer labeling of objects. 
     Another object of the invention is to improve the appearance of heat transfer labels. A related object is to eliminate the enlarged, irregular halo often encountered in heat transfer labeling. 
     A related object is to economize on the amount of material needed for the release layer in the heat transfer labeling of objects. 
     SUMMARY OF THE INVENTION 
     In accomplishing the foregoing and related objects, the invention provides for the use of a thermoplastic release layer containing a repellent material such as silicone. The release layer is contoured in accordance with a prescribed pattern and is in registration with a transfer layer. 
     Since the release layer is contoured, it does not present an irregular appearance. Further the contoured pattern can be made to closely approximate the contour of the transfer layer and thereby significantly reduce the extent of the halo. 
     In accordance with one aspect of the invention the halo can be completely eliminated by having the confines of the transfer layer exceed those of the release layer. 
     In accordance with a further aspect of the invention the release layer is applied by printing, instead of coating the carrier. This significantly reduces the amount of material needed. In addition when the release material is a resin, as opposed to a wax, there is less absorption by the carrier and less material is needed. 
     Printing of the release layer also eliminates the need for a coating operation in conjunction with the printing operation by which the transfer layer is applied to the carrier. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Although aspects of the invention will become apparent after considering several illustrative embodiments taken in conjunction with the drawings in which: 
     FIG. 1A is a plan view of heat transfer label carrier of the prior art; 
     FIG. 1B is a sectional view of the carrier of FIG. 1A; 
     FIG. 1C is a perspective view of an object that has been labeled using the carrier of FIG. 1A; 
     FIG. 2A is a plan view of a heat transfer label carrier in accordance with the invention; 
     FIG. 2B is a sectional view of the carrier of FIG. 2A; 
     FIG. 2C is a perspective view of an object that has been labeled using the carrier of FIG. 2A; and 
     FIG. 3 is a plan view of an alternative heat transfer label in accordance with the invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 1A through 1C of the drawings, a carrier 11 (FIGS. 1A and 1B) in accordance with the prior art is provided with a coating 12 upon which is superimposed a transfer layer 13 which includes a design print. 
     When the transfer layer 13 of the carrier 11 is brought into contact with an object to be labeled, such as the illustrative container 14 of FIG. 1C, and heat is applied, the wax coating 12 melts and allows the contacting portion of the transfer layer 13 to adhere to the container 14. Simultaneously a wax film 15 is deposited on the container 14. This film is of irregular configuration and considerably larger than the transferred design print 16. Under certain viewing conditions the film 15 presents an objectionable appearance. 
     To remedy the foregoing difficulties, the invention provides the heat transfer labeling arrangement of FIGS. 2A and 2B in which a contoured release layer 22 is applied to the carrier 21 and a transfer layer 23 is superimposed on the release layer. As a result, when the transfer layer 23 is brought into contact with an object to be labeled, such as the illustrative container 24 of FIG. 2C, the transferred design print 25 has superimposed on it a release layer which provides a contoured halo 26 with a narrow margin. 
     If it is desired to eliminate even the narrow halo 26, this can be done, as shown in FIG. 3, by forming the heat transfer label with a contoured release layer 32 that is within the confines of a transfer layer 33. When this label is applied to an object the design print from the transfer layer 33 is coextensive with the boundaries of release layer 32. 
     The release layers 22 and 32 are applied to a carrier by printing. For that purpose suitable materials are soluble resins such as polyamides, polystyrenes, rosin derivatives, phenol formaldehydes, terpene resins and ketone resins. Suitable solvents include alcohols and toluenes, and various mixtures of the same. A small amount of glycerine is added to achieve repellency, i.e. non-tackiness in the finished product. A suitable material for the transfer layers 23 and 33 is the resin isobutylmethacrylate, which desirably has a low melt viscosity in the range from 3.5 to 8.5 poises at 160 degrees centrigrade, and a softening point in the range from 95° to 106° C. 
     The practice of the invention is further illustrated with reference to the following non-limiting examples: 
     EXAMPLE I 
     A polyamide resin sold and marketed under the trade name EMEREZ 1538 of Emery Industries was dissolved in 70 parts isopropyl alcohol and 30 parts toluene to form a solution with a concentration of 30 percent resin. To this is added silicone in the range between 1 and 5 percent. The resulting solution is printed in a contoured pattern on a paper carrier of conventional bodystock for heat transfer labeling using a rotogravure press. The print pattern is dried to remove the solvent and overprinted with a transfer layer, formed by an ink lacquer of isobutylmethacrylate, in a contoured pattern in registration with the release pattern. The doubly imprinted carrier stock is used to apply the design print of the ink lacquer to an object to afford good transfer with an insignificant release halo and suitable repellency. 
     Other appropriate polyamide resins of the EMEREZ type are sold and marketed under the trade names EMEREZ 1536 and 1537. 
     EMEREZ polyamide resins have the characteristics illustrated in TABLE I, below. 
     
                       TABLE I______________________________________CHARACTERISTIC EMEREZ 1536  EMEREZ 1538______________________________________Softening point range          95-105       98-106(degrees centigrade)Melt Viscosity 3.5-5.0      6.5-8.5(poise at 160 degreescentigrade)Molten Color   12           10(1963 Gardner)Viscosity in 40% Mixed          66           82Solvent(cps at 25° C.)Viscosity in 40%          62           95n-Propanol(cps at 25° C.)______________________________________ 
    
     EXAMPLE II 
     Example I is repeated using a polyamide sold and marketed under the trade name VERSAMID 940 by General Mills. Satisfactory release is afforded with an insignificant release halo. 
     EXAMPLE II 
     Example I is repeated using a polyamide sold and marketed under the trade name VERSAMID 948. Satisfactory release is afforded. 
     EXAMPLE IV 
     Example I is repeated using a polystyrene resin sold and marketed under the trade name LUSTREX 3 using toluene as the solvent. Satisfactory release is afforded with an insignificant release halo. 
     EXAMPLE V 
     Example IV is repeated with a similar result using a rosin derivative sold and marketed under the trade name PENTALYN A. 
     EXAMPLE VI 
     Example IV is repeated with a similar result using a modified phenol formaldehyde sold and marketed under the trade name AMBEROL F-7. 
     EXAMPLE VII 
     Example IV is repeated with a similar result using a terpene resin sold and marketed under the trade name PICCOLYTE S-100. 
     EXAMPLE VIII 
     Example IV is repeated with a similar result using a ketone resin sold and marketed under the trade name ADVARESIN CXF. 
     It will be understood that the foregoing examples and description are illustrative only and that other examples and equivalents within the spirit and scope of the invention will occur to those skilled in the art.