US3463697A - Reusable transfer medium with print characteristics comparable to filled ink - Google Patents

Description

United States Patent REUSABLE TRANSFER MEDIUM WITH PRINT ICPEIARACTEIRISTHIS COMPARABLE T0 FILLED Hugh T. Findlay and Wiiliam H. Horne, Lexington, Ky.,

assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York No Drawing. Filed Feb. 23, 1966, Ser. No. 529,269

Int. (ll. 1332i) 27 06, 27/34, 9/04 U.S. Cl. 161-465 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to transfer mediums and more particularly to transfer mediums having reuse and good print quality.

Conventional complete transfer typewriter ribbons are usually given body by the inclusion of a substantial amount of wax. Other materials having plasticity, such as synthetic polymers, can also function as the base in such a complete transfer typing medium. The transfer layer contains coloring matter such as carbon black and various dyes. Transfer layers of this kind can be termed filled inks since the plastic material gives a body to the material which is not found in a liquid ink.

The frangible nature of the body material presents many surfaces for light reflectance within the boundaries of a printed character. A desirable sparkle is thereby obtained which often cannot be duplicated by liquid inks. The conventional filled ink also remains on the surface of the copy paper to thereby block the surface in a manner which contributes to opacity. Liquid inks differ greatly in this regard since liquid inks tend to penetrate the paper and are thereby toned down by adsorption on to the White copy paper.

Typewriter ribbons which provide the special print characteristics just described almost always comprise a plastic or paper substrate supporting a layer of a wax or resin based filled ink lightly bonded to the substrate. Those providing the best quality of print completely transfer the ink layer conforming to an image impression to paper or other receptive material and are therefore not capable of reuse. Each successive area of such a transfer medium is generally used, and then the transfer medium must be discarded.

A primary deficiency of the prior art filled ink transfer mediums is therefore complete lack of reusability when the transfer medium is formulated and designed to produce high print quality. It is the primary object of this invention to provide a high print quality typewriter ribbon which can be overprinted and similarly reused a plurality of times. Similarly, it is a general object of this invention to provide a transfer medium having improved characteristics beneficial to reuse of the transfer medium.

Present complete transfer typewriter ribbons often lose or flake off small amounts of their transfer layer as the ribbon is mechanically plied and similarly worked during ribbon feed of the typewriter. These flaked portions can drop into the typewriter, where the pigments contained in them act as destructive abrasives in the typewriter. It is another object of this invention to provide a ice transfer medium carrying a filled ink with improved resistance to the loss or flake of transfer layer material.

In accordance with this invention a transfer medium is devised which has a resinous supporting area, topped by an area of somewhat random mixing of a resin phase and a filled ink phase; the random area merges with and is topped by an outer area containing substantially only a filled ink.

Further in accordance with this invention, a process is devised to achieve the desired product. A layer of resin having substantially no transfer material is supported on a temporary substrate. This layer can be quite thin because the temporary substrate will carry most of the mechanical stresses created in the process. A layer of the filled ink material dispersed in a solvent for the resin of the resin layer is then deposited on the resin layer, and the solvent is then driven off. An intermiXing takes place because the solvent initially dissolves significant amounts of the resin. An excess of filled ink over the amount of ink mixed with the resin dissolved in the process is provided so that a substantial portion of the filled ink will be left on the outer surface. In this manner the product desired is obtained.

The product obtained undoubtedly has some of the filled ink trapped in cavities of the resin in the manner of a spongeous transfer medium similar to that taugh in US. patent application Ser. No. l7l,l88; filed Feb. 5, 1962; titled Transfer Medium and Method for Making Same, on application of H. T. Findlay and K. H. Froman, and assigned to the assignee of this invention (United Kingdom patent specification 965,517 corresponds to this U.S. application). The characteristics of the products herein de scribed in having both a resin phase carrying an ink phase in the manner of a sponge contributes significantly to the reuse characteristics of the product of this invention since the filled ink will move out or exude from the body of the medium under writing pressure.

Also, the outer surface of the resin is undoubtedly jagged and otherwise irregular. This tends to grasp or lock around the filled ink. In this manner the transfer layer is held from working off or flaking during the normal handling of the transfer medium.

The final product obtained is about as thin as the prior art, high print quality, filled ink ribbons. A thin ribbon is benefited both in print quality and by the increased amount of ribbon which can be stored in a typewriter. In the product in accordance with this invention the outer surface has substantially a pure filled ink layer and more filled ink is available from the internal areas of the product. At least the first two strikeovers have been found to be essentially as good in print quality as the print quality obtained by those prior art filled ink ribbons which are considered of the highest quality.

No prior art is known of a type which would render this invention an improvement to a previously existent entity. Certain components of this invention are similar to or otherwise known in the prior art. Thus, the preferred filled ink herein described is similar to prior art filled inks and certain prior art filled inks can be used in this invention without change in formulation of the solid filled inks. The spongeous structures of the product and a few external similarities of the process are the same as that cited in the above referenced application Serial No. 171,188. 'In fact, however, the process herein disclosed operates in a completely novel manner on an ink free resin film. A transfer medium is known in which liquid ink is held in a bulbous material to replenish the liquid ink held in a spongeous transfer layer of a kind similar to the spongeous transfer layer of this invention. In other art, an essentially solid ink within a transfer layer is taught. Reusability of a filled ink containing transfer layer is believed to be an unsolved problem in the prior art, with the immaterial exception of conventional carbon papers, in which the transfer characteristics of the filled ink are very poor.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

To make the preferred product in accordance with this invention, the following liquid ink mixture may be first compounded.

LIQUID INK MIXTURE Parts by weight Carbon black with dye precipitate (Uhlich 1686- Product of Paul Uhlich and Co.) 6 Carbon black with dye precipitate (Uhlich 2451L Product of Paul Uhlich and Co.) 10 Nigrosine oleate (DS 2l83-Product of Dye Specialties Inc.) 63

Methyl violet base (dyestutf) 3 Liquid mixture of fatty acid esters (Kronisol R9 Product of FMC Corp.) 18

The above mixture is compounded by simply combining the components and ball milling for a time required to achieve a complete dispersion. No elevation of temperature is required. The carbon black will be suspended colloidally. The nigrosine oleate is a viscous liquid which dissolves into the fatty acid esters. The methyl violet base is a solid material which dissolves into the fatty acid esters. The dispersion obtained will remain indefinitely without setting or other separation.

All of the components of the liquid ink are either liquid vehicles or imaging materials. The combination selected is one which will produce an intense, dark color, but not the dull black obtained from using carbon black alone as the imaging material. A dispersed, filled ink mixture may then be compounded as follows.

DISPERSED, FILLED INK MIXTURE I Parts by weight Ethyl alcohol (denatured) (laysol Product of AMSCO Solvents & Chemical Co.) 37.5 Liquid Ink Mixture (above formula) High melting point wax (Acrawax C, Atomized A synthetic wax-Product of Glyco Chemical, a division of Chas. L. Muisking & Co., Inc.) 2-3 In compounding the above mixture, the wax is first ball milled into the liquid ink mixture. A blending of this type to achieve a total mixture of two pounds has been achieved with ball milling for two hours. The temperature desirably should be about 120 F., but not substantially above. (This much heat may be generated by the internal friction of the ball mill.) The significant criterion with regard to temperature at this point in the process is that the temperature should be below the melting point of the wax. This blend is essentially the filled ink of this preferred embodiment, and the filled ink will be solidified subsequently by elevating the heat of processing.

The ethyl alcohol is then added to the ball mill. Milling is continued at the 120 F. temperature until a permanent fluid mixture is obtained. With a filled ink mixture of two pounds thus may require two hours of milling.

The wax is not soluble in the alcohol. However, a complete dispersion is obtained. This would be colloidal in nature, at least with regard to the carbon black and the wax. The dyes used are soluble in the alcohol and are believed to function in the dispersion as dispersing agents for the insoluble materials. The dispersed, filled ink mixture will remain indefinitely without settling or other separation.

Final compounding of the product may be by generally conventional apparatus. First a pure, 0.001 inch thick film of alcohol soluble nylon is supported on a temporary substrate. Preferably the temporary substrate is a wide,

pliable roll of polyethylene glycol terephthalate. Preferably a nylon film is applied as a solution by a roll coater in a manner generally similar to that described in the above mentioned application Ser. No. 171,188. The solvent for the nylon is evaporated by heat and air circulation and the polyethylene glycol terephthalate carrying a solid film of nylon 0.001 inch thick is rolled up at the end of the coater. This bulk roll is progressed through the same coater when desired to continue the fabrication of this preferred embodiment.

Thus, to apply the filled ink, the nylon supported on the temporary substrate is moved for coating of the nylon by the roll coater. The coating mixture is the dispersed, filled ink mixture above described. It is applied by the applicator roll in quantities of 7 pounds per ream (500 20" x 30" sheets) of nylon. The temporary substrate moves continuously to almost immediately carry the coated nylon into a drying environment. In the drying environment the surrounding air is circulated vigorously and the temperature is initially kept at F. for about one minute. The temperature is then raised to 220 F. for one minute. This completes the drying.

During drying, the alcohol is expelled. Prior to that expulsion, however, the alcohol partially dissolves the nylon (without the temporary substrate the nylon would fail under the stresses of movement in the system). Furthermore, the heat of the drying environment is above a critical point with relation to the wax-liquid ink mixture. An internal reorganization of some kind takes place causing the mixture to solidify.

The temporary substrate carrying bulk quantities of the finished transfer medium is rolled into a large roll. The transfer medium may be easily grasped and peeled or separated from the polyethylene glycol terephthalate. After such separation, the transfer medium may be slit and rolled into typewriter ribbons or cut a otherwise desired.

The final product is a unitary film of about 0.0015 inch thick. One side of the film is essentially pure nylon. This is desirable to add cut resistance to the transfer medium and to prevent the expression of ink from the impacted side of the transfer medium. (A finely divided, inert filler could be added to the pure nylon if, for example, a stiffer ribbon is desired.) Within the transfer medium the filled ink is situated in cavities and openings, or voids. On the side opposite the pure nylon a layer of essentially pure filled ink without nylon approximately 0.0005 inch thick exists. The voids communicate filled ink to the side holding the filled ink. The surface of the nylon facing this filled ink layer is doubtless somewhat rough, and doubtless projections of the nylon enter into this essentially pure filled ink layer to a significant extent.

During normal use as a typewriter ribbon the ribbon is clean handling. Only negligible amounts of the transfer material dislodge or flake into the typewriter. The primary significant factor is that at least two overstrikes of the same ribbon area will both produce a print quality comparable in quality with the best commercial filled ink ribbons presently available. The quality is good even with further reuse of the ribbon, up to usually four or five reuses.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A process to prepare a transfer medium comprising the steps of:

supporting a layer of resin on a temporary substrate,

forming a filled ink mixture by mixing a liquid ink,

said liquid ink comprising coloring material dispersed or dissolved in a liquid vehicle, and particles of a high melting point wax with a solvent for said resin at a temperature below the melting point of said Wax, said solvent being a non-solvent for said wax such that said wax particles are dispersed in said solvent,

depositing a coating of said mixture on said resin such that said solvent dissolves significant amounts of said resin and the dissolved resin and said filled ink intermix,

heating said coating above the melting point of said Wax to expel said solvent and to form a void containing intermediate layer on the outer surface of said resin layer, at least some of the voids contain ing a filled ink which will exude from said resinous layer under writing pressure,

forming a substantially completely transferable outer layer of substantially pure filled ink approximately 0.0005 inch thick on said intermediate layer by providing an excess of filled ink over the amount of ink mixed with the dissolved resin, and

stripping said transfer medium from said temporary substrate to obtain a transfer medium which upon initial use has a substantially completely transferable outer layer providing the high write quality of a filled ink, complete release type transfer medium which is normally non-reusable but which medium by the presence of said solvent has an intermediate transfer layer which will produce a write quality upon reuse which is equivalent to the write quality of said outer layer.

2. The process as in claim 1 in which said rosin comprises a major part of nylon, said solvent is ethanol, and said ink includes a significant amount of carbon black and contains less than half by weight of said wax.

3. A transfer medium produced by the proces comprising the steps of:

supporting a layer of resin on a temporary substrate,

forming a filled ink mixture by mixing a liquid ink,

said liquid ink comprising coloring material dispersed or dissolved in a liquid vehicle, and particles of a high melting point wax with a solvent for said resin at a temperature below the melting point of said wax, said solvent being a non-solvent for said wax such that said wax particles are dispersed in said solvent,

depositing a coating of said mixture on said resin such that said solvent dissolves significant amounts of said resin and the dissolved resin and said filled ink intermix,

heating said coating above the melting point of said wax to expel said solvent and form a void containing intermediate layer on the outer surface of said resin layer, at least some of the voids containing a filled ink which will exude from said resinous layer under writing pressure,

forming a substantially completely transferable outer layer of substantially pure filled ink approximately 0.0005 inch thick on said intermediate layer by providing an excess of filled ink over the amount of ink mixed with the dissolved resin, and

stripping said transfer medium from said temporary substrate to obtain a transfer medium which upon initial use has a substantially completely transferable outer layer providing the high write quality of a filled ink complete release type transfer medium which is normally non-reusable but which medium by the presence of said solvent has an intermediate transfer layer which will produce a write quality upon reuse which is equivalent to the write quality of said outer layer.

4. The transfer medium as in claim 3 in which said ink contains less than half by weight of said wax said solvent is ethanol and said resin comprises a major part of nylon.

References Cited UNITED STATES PATENTS 3,037,879 6/1962 Newman et all 117-36.1 3,080,954 3/1963 Newman et al 117-36.4 3,102,824 9/1963 Newman 117-36.1

MURRAY KATZ, Primary Examiner U.S. Cl. X.R.

Ill-36.4, 138.8, l61-227, 234', 264-171, 245