US 3337361 A
Description (OCR text may contain errors)
Aug. 22, 1967 c. H. LA COUNT 3,337,361
PROCESS OF MAKING PRESSURE SENSITIVE TRANSFER SHEET Fil ed Jan. 6, 1964 DISPERSING AGENT LuBRIcATINB COMPOSITE COAT'NG UNli MLY I (EMULSION) P'GMENT COLORING MATTER uNwIND COATING DRYING I FLEXIBLE SPREA N EVAPORATION OF wATER EouNDATIoN T N R 7 BY HEAT 8. MOVING AIR SHEET LA E oIL LUBRICANT sEPARATEs (A MYLAR) To FouNDATIoN SHEET REwIND FUSING PRESSURE BINDER FUSED SENSITIVE INTo CONTINUOUS TRANSFER FILM-BY HEATED RoLL, SHEET lNFRA-RED 0R BOTH WAX COATING LuBRIcATINC CONTAINING oIL LAYER PIGMENT PARTICLES FOR RELEASE INVENTOR; CLRENCE H. LUCQUNT ATTORNEY l United States Patent 3,337,361 PROCESS OF MAKING PRESSURE SENSITIVE TRANSFER SHEET Clarence H. La Count, Rochester, N.Y., assignor, by
mesne assignments, to Kee Lox Manufacturing Company, Rochester, N.Y., a corporation of Pennsylvania Filed Jan. 6, 1964, Ser. No. 336,062 2 Claims. (Cl. 117-36.1)
The present invention relates to pigmented pressuresensitive transfer coatings, and to a process for making the same. More particularly, the invention relates to pigmented pressure-sensitive transfer coatings suitable for applications requiring complete release or transfer of the coating from the carrier sheet under the impact of type or from pressure of a stylus or the like. In a still more specific aspect, the invention relates to pressure-sensitive transfer coatings such as may be used in the printing or encoding of paper records, such as checks, bank deposit slips, etc., with magnetic symbols which can be recognized by electronic accounting equipment, and such as may be used in the manufacture of the so-called onetime carbon ribbons or papers.
Transfer media of the character described are customarily made from a mixture of wax, oil and colorant applied to the base sheet in a hot fluid condition. To provide flow and softening action with high pigment loadings, a high portion of non-volatile plasticizing oil is required. Because of the high oil content, however, waxy coatings applied by the conventional hot melt methods are soft and easily smeared when subjected to the actions of rollers in encoding machinery and to ordinary handling. Moreover, the impressions tend to be non-uniform in thickness and over-size in width because the coating tends to squeeze out or spread upon impact of type or stylus. Furthermore, incomplete release of the coating is often encountered.
One object of the present invention is to provide a pigmented, pressure-sensitive transfer coating which will produce sharp, uniform, and non-smudging impressions.
Still another object of the invention is to provide a pressure-sensitive transfer coating which will produce impressions that are more readily legible than impressions produced from conventional transfer media particularly of the magnetic type.
Another object of the invention is to provide a pigmented, pressuresensitive transfer coating containing practically no oily plasticizer.
Another object of the invention is to provide a pigmented, pressure-sensitive transfer coating from a water emulsion or dispersion.
Another object of the invention is to provide a process for making a transfer coating having the desirable properties mentioned above, and more particularly, a process for applying at room temperature a uniform thickness of pressure transferable material to a base carrier, which can readily be hardened sufliciently to prevent smearing.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.
With the present invention a transfer coating is employed which comprises a Water dispersion of an inert colored pigment, a hard, fracturable binder resin, and a water-miscible, essentially non-volatile liquid lubricant which is incompatible with the binder. The binder may be in the form of a hard, high melting wax.
One Way of practicing the invention, and the article produced are illustrated in the attached drawing, in which:
FIG. 1 is a flow diagram illustrating one method of practicing this invention; and
FIG. 2 is a fragmentary cross-sectional view of a sheet having a pressure transferable coating embodying the invention.
A present preferred coating for use in printing or encoding of paper records such as checks, bank deposit slips, etc, comprises a mixture of modified oxidized Fischer-Tropsch wax having a melting point between 205 F. and 215 F., emulsifiable polyethylene having a ball and ring softening point of C. (221 F.), an ester wax having a melting point of between 176 F. and 181 R, an anionic dispersing agent, magnetic iron oxide, and a polyethylene glycol having an average molecular weight of 400, and water. These ingredients are mixed together by weight in the following manner: to 61.0 parts of a water slurry containing 66% magnetic iron oxide by weight is added 5.75 parts of polyethylene glycol, and 48.0 parts of a Wax dispersion containing 5.0 parts of the modified Fischer-Tropsch wax, 3.0 parts of emulsifiable polyethylene, 2.0 parts of ester wax, 1.5 parts of an anionic dispersing agent and 36.5 parts of water. The transferable coating 10 is applied to-a base carrier 11 at room temperature by any of the common coating methods, for example, wire-wound rod, reverse roll, or knife. Water is removed from the wet coating by infra-red or convection heating; and the dried coating is subsequently melted and fused by means of a heattreatment at a temperature close to the melting point of the wax. The temperature used may vary from to 240 F., depending upon the melting point of the particular wax employed, and also upon the ability of the base film to withstand heat. During the heat treatment a liquid film 12 of polyethylene glycol forms adjacent to the base 11. It is this fihn of lubricant which makes it possible to achieve the sharp, uniform, and non-smudging impressions which are a characteristic of transfer media produced according to this invention.
The preferred base carrier to which the coating is applied is polyethylene terephthalate, commonly called Mylar; although other bases may be used. For example, paper treated so as to permit water-based coatings, cellulosic films, rubber hydrochloride, polyethylene and polypropylene are acceptable bases.
The preferred binder is a Water dispersion of high melting waxes (ester waxes). However, water dispersions of polymers made from a mixture of straight chain and cyclic hydrocarbons are acceptable.
A variety of pigments and fillers may be used depend ing upon the end use of the transfer medium, For example, carbon black dispersions have been used to make a single-use typewriter ribbon; and such dispersions may be used in place of the magnetic iron oxide in the mixture 3 above described.
Classes of compounds, which have been used successfully as lubricants, include the polyols, glycols, in particular ethylene and polyethylene glycols, and organosilicone fluids. The lubricants in general must be substantially incompatible with the binder, must be miscible or dispersible in water, and must be essentially nonvolatile.
There is substantial latitude in the relative amounts of ingredients used. For instance, the coating may comprise 29 to 35 parts by weight of black iron oxide, 15 to 10 parts by weight of wax, 6 to 5 parts by weight of a liquid lubricant, and 50 parts by Weight of water. Small percentages, 1 to 2% of other ingredients such as watersoluble thickeners and auxiliary binders may be added to provide suspending action for pigments and sharper printing qualities, respectively. Part or all of the magnetic oxide may be replaced by neutral or basic pigments. The wax binder is in emulsion form and preferably contains approximately 13% (of total) of ,an amine soap emulsifier. However, other emulsifiable binders, similar to wax, may be used.
The excellent transfer properties exhibited by this coating are apparently due to the fact that on removal of water from the coating by infra-red or convection heating, and subsequent melting and fusing together of the wax emulsion particles, the residual liquid lubricant separates physically from the wax-pigment layer and forms adjacent to the base. This separation occurs because wax, and certain water-soluble materials are substantially, if not completely, incompatible when both are in the liquid phase. This incompatibility causes the lubricant to transfer to the base instead of to the surface of the coating. The mechanism by which this is accomplished is not fully understood but is believed to be due to the following:
(a) The lubricant tends to concentrate at the base during removal of water prior to the fusing operation. Because the coating is on an impervious film base, it dries from the surface down; and the lubricant migrates to the base. The separation of the lubricant at this point is not sufficient to provide adequate transfer properties. This is achieved by the melting and fusing step produced by the heat treatment.
(b) The specific gravity of the lubricant is substantially greater than most waxes and may help to explain the separation into two layers.
Melting and fusing takes place in a fraction of a second at a temperature close to the melting point of the wax used. The minimum fusing temperature is 190 to 200 F. It may be possible to use Waxes, mixtures of waxes, or wax-like materials which will fuse at lower temperatures. The hard, high melting synthetic and natural waxes in general are more smear-resistant and provide better transfer than the softer, lower-melting waxes.
While the invention has been described in connection with several different embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features here inbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.
Having thus described my invention, what I claim is:
1. A process for making a pigmented pressure-sensitive transfer medium containing practically no oily plasticizer, comprising mixing 61.0 parts by weight of a water slurry containing 66% magnetic iron oxide and 5.75 parts by weight of polyethylene glycol with 48.0 parts of a wax dispersion containing 5.0 parts of modified Fischer- Tropsch wax, 3.0 parts of emulsifiable polyethylene, 2.0 parts of ester wax, 1.5 parts of an anionic dispersing agent and 36.5 parts of water, coating a base carrier with said mixture at room temperature, removing the water from said coating, and melting and fusing the remainder of the coating thereby to form a liquid fihn of polyethylene glycol adjacent the base.
2. A process for making a transfer medium comprising depositing on a water impervious base a pigmented, pressure-sensitive transfer coating containing practically no oily plasticizer, said coating comprising a water slurry containing a pigment, a binder, and a lubricant which is substantially incompatible with the binder, which is miscible or dispersible in water, which is non-volatile, and which has a specific gravity greater than the binder, removing water from the coating to dry it, and then subjecting the dried coating to a heat treatment to melt and fuse it and to cause a thin film of the lubricant to form between the base and the remainder of the coating thereby to constitute a transfer layer, said binder being a wax in emulsion form, and said lubricant being selected from the group consisting of ethylene glycol and polyethylene glycol and having a specific gravity greater than the wax.
References Cited UNITED STATES PATENTS 1,328,188 1/1920 Ohashi 1l7--36.l XR
2,866,711 12/1958 Hart l1736.1 XR 3,029,157 4/1962 Sutheim et al. l1736.1XR
3,151,550 10/1964 Newman 11736.1 XR 3,214,285 10/1965 Wissinger et al. 117-36.4
OTHER REFERENCES Anderson: IBM Technical Disclosure Bull, vol. 5, No. 4, September 1962.
MURRAY KATZ, Primary Examiner.