HEAT-SENSITIVE COPY SYSTEM

Abstract: A heat-sensitive copy system including a pair of superimposed sheets (10, 14), one of which (10) has a coating (20) on one surface thereof, which coating is sandwiched between the sheets. The coating includes a thermochromic dye, a phenolic material and a polyterpene resin binder which becomes tacky when heated by thermal printing means causing coating material to adhere to the uncoated sheet (14) thereby to produce similtaneously an image (22) on the two sheets (10, 14) according to the applied heat pattern.

Description: HEAT-SENSITIVE COPY SYSTEM Technical Field .The present invention relates to a heat- sensitive copy system and, in particular, to a copy system for making an original and copy during a printing operation. Background Art In the field of thermal printing, it is well- known that a significant limitation in the printing operation is the absence of copies during such printing operation. The early thermal printing systems used a thermal print element energized to heat specific and precise areas of a heat-sensitive paper or like record material and thereby produce readable characters on the single sheet of paper. In this respect, the single sheet of paper includes material which is reactive to the applied heat and is described as a self-contained system. More recently, thermal printing systems have included two separate sheets of paper or like record material, wherein each sheet is coated with a heat- sensitive reactive material. The top or front sheet is usually a light weight tissue-type paper which is coated with the heat-sensitive material and the second sheet is preferably bond-type paper which is also coated with the sensitive material. The two sheets are then mated or collated in a manner wherein the uncoated side of the tissue paper is in contact with the coating on the bond paper. The coated side of the tissue paper is adjacent and in close proximity to the thermal printing elements, or in certain applications, the elements may be in actual contact with the tissue paper. The thermal elements are actuated to provide specific and precise marking or imaging on the papers in the process which enables the obtaining of a master sheet plus a readable copy. OWPI Alternatively, the tissue paper could be coated on both the front and back sides so that the thermal printing elements are adjacent or in contact with the front coated side of the tissue paper and the back coating is in contact with the bond paper. In similar manner, the thermal elements are actuated to provide the specific and precise marking or imaging on the two papers so as to be in readable form. The tissue sheet and the bond sheet are arranged in manifold manner and the imaging is accomplished by transfer of the ink or like material in the coating onto the sheet. A heat-sensitive copy system in which ink in the coating of one sheet is transferred to another sheet is disclosed, for example, in U.S. Patent No. 3,539,375. In one embodiment of this system, a transfer sheet has a coating including a chromogenic material, such as cry¬ stal violet lactone, and a phenolic material disposed in a matrix of polyvinyl alcohol and arranged such that application of heat produces a pattern of mobile col- oured fluid which is transferred to a plain sheet of paper placed in contact therewith. Another transfer system is disclosed in U.S. Patent No. 3,561,991 in which the transfer sheet has a coating including a chromogenic material and a phenolic material in a finely divided plasticizer and an adhesive butylene material. Applied heat brings about a colour reaction and melts the coating in accordance with the heat pattern.. The coating material remains soft and tacky in the heat image area for a considerable time during which several copies of the printed data may be taken by copy sheets pressed against the transfer sheet. It should be noted that the polyvinyl alcohol binder of the first mentioned U.S. patent is relatively non-tacky when heated, whereas the adhesive butylene material of the second U.S. patent provides a coating which remains tacky for a period measured in tens of minutes. Disclosure of the Invention It is an object of the present invention to provide a low-cost heat-sensitive copy system in which the transfer sheet has a coating whose composition is so chosen that, when heated, it provides a tackified con¬ dition of a predetermined and precise nature suitable for obtaining a two copy printing or imaging of data. Thus, according to the invention, there is provided a heat-sensitive copy system including a pair of superimposed sheets, one of said sheets having on one surface thereof a coating which is sandwiched between the two sheets and which includes a thermochromic dye, a phenolic material and a binder, characterized in that said binder includes a polyterpene resin material which becomes tacky when heated by thermal printing means causing coating material to adhere to the uncoated sheet thereby to produce simultaneously an image on the two sheets according to the applied heat pattern. In a preferred embodiment of the invention, the composition of the heat-sensitive coating includes a thermochromic dye, a phenolic resin and a synthetic polyterpene binder. The coating is provided on one record sheet such as paper or the like, and the coated sheet is then mated or collated with an uncoated sheet in a manner wherein the coating material is sandwiched between the sheets. In more specific language, the top or front record sheet is a tissue or translucent type paper and such sheet is coated with the improved thermochromic or heat-sensitive material on the back side thereof, which material is in contact with the front side of the rear record sheet, preferably a bond or like paper. The two sheets are imaged by use of thermal printing elements being placed in extremely close proximity or in actual contact with the uncoated or front side of the tissue sheet and heat emitted from such printing elements is transferred through the tissue sheet and onto the bond O PI sheet resulting in a transfer of some coating from the back side of the tissue sheet to the uncoated bond sheet and thereby producing an image or mark on both sheets. The image can be read from the front of both sheets in normal manner. An alternate method of transferring the mater¬ ial for the purpose of making a copy of the image or mark is to provide a coating of the improved thermo¬ chromic material on the front of the bond sheet, which sheet is placed rearward of the tissue sheet. The coating material is then sandwiched between the uncoated tissue sheet and the front surface of the bond sheet and the imaging is accomplished by transferring some of the coating from the bond sheet to the back side of the tissue sheet upon application of heat by thermal print¬ ing elements placed in contact or in extremely close proximity with the front of the tissue sheet. Brief Description of the Drawings Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figs. 1 and 2 are diagrammatic views of ther¬ mal copy systems as exemplified in the prior art; Fig. 3 is a diagrammatic view of a preferred thermal copy system of the present invention; Fig. 4 is a diagrammatic view of a modified thermal copy system of the present invention; Fig. 5 is a diagrammatic view of the record sheets of Fig. 3 and showing the transfer of the thermal material; and Fig. 6 is a diagrammatic view of the record sheets of Fig. 4 and showing the transfer of the thermal material. Best Mode for Carrying Out the Invention • Referring to the drawing. Figs. 1 and 2 show conventional two copy, thermal paper systems wherein each paper contains a coating on one surface thereof, Fig. 1, or the front paper contains a coating on both the front and back surfaces thereof, Fig. 2. In Fig. 1 a front sheet 10 includes a coating 12 on the face thereof and a back sheet 14 has a coating 16 on its front surface. A thermal print element 18 is positioned for marking or causing marking on the sheet 10 and enabling the carrying of the marking onto the sheet 14 by heating the coating 12 and imaging such marking on the coating 16. While sheets 10 and 14 are shown apart and separate from each other, both sheets are in actual practice in mating contact, and it is seen that the uncoated side of sheet 10 is against the coating 16 of sheet 14 and the coated side of sheet 10 is against the print element 18. A conventional assembly is construc¬ ted with an arrangement wherein sheet 10 is a light weight, tissue-type, paper and the sheet 14 is a bond- type paper. In Fig. 2 the sheet 10 has the coating 12 on the front side and the coating 16 on the back side thereof, whereas the bond sheet 14 is uncoated. When the thermal print head 18 is energized, the heating of the coating 12 causes marking on the sheet 10 and the heat is carried through the tissue sheet to transfer some of the coating material 16 onto the sheet 14 re¬ sulting in both sheets being imaged to provide a read¬ able two-copy system. Fig. 3 illustrates in diagrammatic form the concept of the present invention wherein the tissue-type paper 10 adjacent the print head 18 includes an improved coating 20 on the back side thereof for mating with the front side of the uncoated bond paper 14. The heat from the print head 18 carries through the tissue sheet 10 causing transfer of some of the coating 20 onto the front of the bond sheet 14, with the result that an image or mark is produced on both sheets and both sheets are readable from the front sides thereof. Fig. 4 illustrates a modified system wherein the front sheet 10 is uncoated and the bond sheet 14 includes the improved coating 20 on the front surface. The coating 20 is sandwiched between the two sheets 10 and 14 and the imaging technique is accomplished during heating of the sheet 10 by transferring some of the coating 20 from the front surface of the bond sheet 14 onto the back surface of the tissue sheet 10. Fig. 5 shows the tissue sheet 10 and the bond sheet 14 with the improved coating 20 on the back side of sheet 10 and the marking is transferred onto sheet 14 as an image 22 upon application of heat. In similar manner, Fig. 6 illustrates the improved coating 20 on the front surface of sheet 14 and transfer of a portion of the coating onto the back side of sheet 10 to accom¬ plish the mark or image 22 thereon. The present invention provides for applying and using the thermochromic coating on either the tissue sheet 10 or on the bond sheet 14— nd transferring a portion of the coating 20 onto one or the other uncoated sheet upon actuating the heating element 18 during the imaging operation. EXAMPLE I Example I describes the method wherein a coating 20 of thermochromic material is applied to the back surface of trie translucent tissue sheet 10 and such sheet is mated or collated with the uncoated bond sheet 14 so that the coating material 20 is sandwiched between the front surface of the bond sheet and the rear surface of the tissue sheet, as illustrated in Fig. 3. The two sheets 10 and 14 are then imaged by the heating element 18 being placed in contact with the uncoated or front side of the tissue sheet 10. The heat from element 18 is transferred through the tissue sheet 10 and onto the bond sheet 14 resulting in some of the coating 20 being " πpδ transferred from the back side of the tissue sheet and carried to the uncoated bond sheet, thereby producing an image on both sheets 10 and 14 which can be read from the front of each sheet in normal manner. EXAMPLE II Example II describes the method wherein a coating 20 of thermochromic material is applied to the front side of the bond sheet 14 and such sheet is mated or collated with the uncoated tissue sheet 10 so that the coating material 20 is sandwiched between the back surface of the tissue sheet and the front surface of the bond sheet, as illustrated in Fig. 4. The two sheets 10 and 14 are then imaged, as described in Example 1, except that the coating 20 is transferred to the trans- lucent sheet 10 from the coated bond sheet 14. COATING COMPOSITION The thermochromic coating formulation consists of a thermochromic dye, a phenolic resin, one or more waxes and a binder. A preferred coating composition is as follows: Percent Material Trade Name Dry Weight Crystal violet lactone 6.0 Phenolic resin Parabis 28.0 Ceresin wax 27.5 Mixture of octa, hexa, Armid HT 27.5 penta, 9-octa decanamide Synthetic Polyterpene Wingtack 95 10.0 Octadecyl 3,5-di-tert- Irganox 1076 1.0 butyl-4-hydroxy- hydracinnamate Preferably, the amount of polyterpene resin material to the thermochromic dye and phenolic material is 25% to 35%, by weight. A preferred phenolic material is formula 4 , 4 ' isopropyli- denediphenol having the trade name Parabis and of the structure CH-, An alternate dye for use with the Parabis phenolic resin is 2 '-analino-6 '-diethylamino-3 ' -methyl fluoran having the trade name N102 and of the structure The synthetic polyterpene is mixed with the lactone and the resin and binds these materials into a composition which becomes tacky upon the application of heat. The tacky condition or characteristic of the bound coating influences and accelerates transfer of some of the coating to the mating sheet for good adher¬ ence thereto during the printing operation. OM .Λ, W.F Referring back to the materials mentioned above in the coating composition, the thermochromic dye (cry¬ stal violet lactone or methyl fluoran) is available from Hilton-Davis Company, Cincinnati, Ohio. The phenolic resin, sold under the trade name Parabis, is available from Dow Chemical Company, Midland, Michigan. The cere- sin wax or "a similar ozokerite mineral wax are readily available products. The decanamide mixture is an amide wax sold under the Armid HT trade name by Armak Chemical Division, Chicago, Illinois. The polyterpene is avail¬ able as Wingtack 95 from Goodyear Chemical Company, Akron, Ohio. And, the cinnamate is an anti-oxident available under the trade name Irganox 1076 from Ciba- Geigy, New York, New York. The polyterpene in the coating composition and in the appropriate percentage of the total weight there¬ of, as noted in the above table of materials, is formu¬ lated to provide the best mode for carrying out the invention.-—.The coating composition or formulation provides a tackified condition of a predetermined and precise nature in an area or range between a non-tacky condition and an extremely tacky condition. The poly¬ terpene enables the transfer of the dye material from one sheet to the other sheet at low energy levels by reason of the herein-disclosed and preferred tackified coating that results in good adhesion to the receiving sheet upon the application of heat during the printing operation. The present invention thus utilizes one coated sheet to provide a process for obtaining two copy printing or imaging of characters. O PI

Claims: CLAIMS : 1. A heat-sensitive copy system including a pair of superimposed sheets (10, 14), one of said sheets (e.g. 10) having on one surface thereof a coating (20) which is sandwiched between the two sheets (10, 14) and which includes a thermochromic dye, a phenolic material and a binder, characterized in that said binder includes a polyterpene resin material which becomes tacky when heated by thermal printing means causing coating mater¬ ial to adhere to the uncoated sheet (14) thereby to produce simultaneously an image on the two sheets (10, 14) according to the applied heat pattern. 2. A copy system according to claim 1, characterized in that one of the sheets (10) is a trans¬ lucent sheet having the coating (20) on the reverse side thereof. 3. A copy system according to claim 1-, characterized in that one of the sheets (14) is a bond sheet having the coating (20) on the front side thereof. 4. A copy system according to claim 1, characterized in that the polyterpene resin material is a synthetic polyterpene approximating 10% by weight of the coating. 5. A copy system according to claim 1, characterized in that the relative amount of polyterpene resin material to the thermochromic dye and phenolic material is 25% to 35%, by weight. 6. A copy system according to claim 1, characterized in that the thermochromic dye is crystal violet lactone. 7. A copy system according to claim 1, characterized in that the phenolic material is 4,4'- isopropylidenediphenol. 8. A copy system according to claim 1, characterized in that the thermochromic dye is 2'- anilino-6'-diethylamino-3'-methyl fluoran.

Inventors: LAKES STEPHEN D, LEWIS MAURICE W, LAKES, STEPHEN, D., LEWIS, MAURICE, W.
Applicants: NCR CO, NCR CORPORATION
Application year: 1984
Main classification: B41M5
IPC codes: B41M5