US3406137A - Imaging material - Google Patents

Description

United States Patent 3,406,137 IMAGING MATERIAL Jack H. Terry, Pittsford, N.Y., and Herbert N. Johnston and Rexford W. Jones, Columbus, and Helmuth 0. Schoen, Worthington, Ohio, assignors, by direct and mesne assignments, to Xerox Corporation, Rochester, N.Y.. a corporation of New York No Drawing. Filed Apr. 29, 1965, Ser. No. 451,960

9 Claims. (Cl. 260-285) ABSTRACT OF THE DISCLOSURE A novel pressure transfer ink formulation comprising a greater amount of pigment and polysiloxane and lesser amounts of waxes, wax soluble dyes, and an adhesive resin, as well as a method of preparing said formulation is disclosed.

This invention relates to an image pressure transfer duplicating technique and, more particularly, to an ink formulation adapted for use therein.

Various techniques have been developed for making multiple copies of original documents by the transfer of a relatively dry imaging material or ink. Perhaps the most well known of these techniques involves the use of an ordinary sheet of carbon paper between the original and a copy sheet in a typewriter. As is well known, this technique of making duplicates of an original typed document suffers from many drawbacks. For example, the carbon paper itself is easily smudged and tends to dirty the hands and clothing of the operator. In addition, because the ink on the carbon paper must transfer readily from the paper sheet under the application of pressure, it also tends to smudge and spread on the duplicates producing fuzzy, illegible and nonpermanent images on the copy sheet. Generally, only a few copies are possible because it is extremely difficult to transmit the pressure of the typed character throughout the whole thickness of the sandwich formed by the carbon sheets and the copy papers so that the readability of the carbon copies most remote from the typed characters drops off drastically. It is also very laborious to make corrections on carbon copies since each copy must be individually corrected.

In order to overcome the many difficulties inherent in the production of duplicates with carbon paper, outlined above, a number of duplicating techniques have been developed such as spirit duplicating, mimeograph, offset and the like. Although some of these techniques produce copies which are vastly superior to carbon copies, they are somewhat more expensive than the use of carbon paper for short runs, sometimes involve messy liquids, and require the typing of a separate master apart from the original. Although duplicating techniques which utilize a master are capable of producing copies at a relatively low cost which is even competitive with carbon copies when a large number of copies are reproduced, the time required and cost of materials involved in producing a master with these processes requires that the master making cost be amortized over a large number of copies. In addition, present day duplicating techniques require a fairly large capital investment in equipment while no such investment is required in making carbon copies. Accordingly, these techniques become prohibitive in cost if they are used to produce less than about twenty copies. In

3,406,137 Patented Oct. 15, 1968 ice summary then, it may be said that there is not available at the present time any process for making a relatively small number of duplicates of an original document with simple, inexpensive apparatus which is competitive in price and yet still superior in quality to carbon copies.

Now in accordance with the present invention there is provided an extremely simple duplicating process for making copies from an original directly by pressure transfer. This technique involves typing the original with a ribbon bearing an ink which is specially adapted to the process, placing the original in face-to-face contact with a transfer sheet and pressing the two together as with a pair of rollers so as to transfer a portion of the original ink to the transfer sheet. After separation of the transfer sheet and original, which leaves a portion of the original ink on each of these two members, the ink transfer sheet is pressed in face-to-face contact with the copy sheets so as to transfer a portion of the ink on the master to each of these copy sheets and form a rightreading duplicate of the original on them.

' Although similar duplicating techniques have been proposed as, for example, in German Patent No. 646,530 and U.S. Patent 3,122,094, pressure transfer duplicating techniques of this type have never become commercial because of the extremely severe requirements which this type of duplicating process places on the ink. First of all the ink must have good transfer properties under the high rates of shear applied to the ribbon during the original typing operation so that sharp, clear letters are produced on the original which will not spread or smudge to any appreciable extent. This alone is quite difficult because a much heavier coating of ink must be applied from the ribbon during the original typing operations so that adequate ink will be present on the original to carry out the duplicating process. In addition, a large portion of the ink once transferred to the original must be capable of being transferred under the much lower rates of shear applied when the original is pressed in faceto-face contact with the transfer sheet and passed between a pair of pressure rollers. Then, a portion of the ink on the transfer sheet is retransferred to successive copy sheets by passing them between the pressure rollers in face-to-face contact with the transfer sheet. These copies must have high resolution and density, imperceptible smudging and little or no tendency for the ink to retransfer to the hands of a person picking up the copy.

The use of heretofore known inks in the processes described in the above-noted patents has resulted in poor image quality together with undesirable transferability and permanency of image. If it is desired to make a minimum of about five copies by the described pressure transfer process, already existing inks, in a number of instances, have been found to be totally unsuitable.

It is therefore an object of this invention to provide a novel ink formulation devoid of the above-noted disadvantages.

Another object of this invention is to provide a novel ink formulation adapted for use in pressure transfer imaging.

Still another object of this invention is to provide an ink adapted for use in a pressure transfer process whereby increased transferability of the image is accomplished.

Another still further object of this invention is to provide a novel process for making an ink formulation adapted for pressure transfer.

Yet another object of this invention is to provide an ink formulation whereby the number of images transferred in a given pressure transfer process is significantly increased.

Yet still another further object of this invention is to provide an ink formulation for pressure transfer capable of producing a high number of copies of good quality.

The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a novel ink formulation adapted for use in a pressure transfer process which comprises.

Ingredient: Formula, parts by weight Pigment 33-72 Wax soluble dyes 2-10 Waxes 3-11 Adhesive resin 3-10 Polysiloxane 25-50 Although good results are obtained using the general formulation above, from fifteen to twenty copies can be made with the preferred and optimum formulations given below.

As indicated by the formulation above, the use of three different pigments has been found to produce exceptionally good results since the various pigments are of difierent sizes and are used in ratios to provide maximum packing density which gives better density and more smudge resistance. Too much pigment results in lower resolution and increased smudging. On the other hand, if too little pigment is used, the proper density cannot be maintained. Any suitable pigment material may be used depending upon the eifect and color desired. Typical pigments are carbon black, black and red iron oxide of the magnetic and non-magnetic types, chromium oxide, chrome yellow and green, toluidine red toner, phthalocyanine, molybdates and iron blues, zinc powder, bronze powder, aluminum powder, and mixtures thereof. Fillers such as barium sulfate and graphite flour can also be used and are comprehended within the term pigments.

Mixing a small amount of wax soluble or wax dispersible dyes in the ink formulation increases uniformity, since the dye colors areas inside of the characters which may be coated only with clear wax or other portions of the ink vehicle. Selective balancing of the amounts of Waxoline blue and Waxoline black is important since undesirable coloring and bleeding results if the portions deviate from that used in the formula above. Any suitable dye, in lieu of or in addition to the waxolines mentioned above, may be used in the ink formulation. Typical wax soluble dyes are Victoria blue (C H N HCl), Methyl Violet (methylrosaniline chloride), Nigrosine Base NB and mixtures thereof.

A combination of waxes, a silicone such as dimethylpolysiloxane gum and adhesive resin provides a vehicle or binder with the desired rheological properties for the ink formulation. The waxes, resin and silicone form an incompatible but uniform and homogeneous mixutre that fractures easily without spreading under high rates of shear and yet permits partial transfer under low rates of shear. When it is recalled that in the pressure transfer process initial transfer of almost the whole ink layer is normally by a high shear rate typing action and subsequent partial transfers are by a low shear rate roller action, the necessity of the foregoing characteristics becomes apparent. For brevity, the ability of the ink to fracture and almost wholly transfer under high shear rates without spreading and flow under low shear rates hereinafter will be referred to as its dilatancy.

Suitable wax materials in sufiicient quantity provide an excellent dispersing medium for the pigment particles. As the softer wax, beesway plasticizes the harder microcrystalline Wax thereby enhancing the transferability desired. Other suitable waxes may be substituted for the microcrystalline wax and beeswax in the formulation above. Typical waxes are parafiin, ouricoury wax, polyethylene wax mixtures, candelilla wax, hard microcrystalline wax which is mixed with plasticizers, such as, mixed cresyl diphenyl phosphates and mixtures thereof.

The inclusion of an adhesive resin reduces smudging by improving the oveall cohesion of the ink formulation. Any suitable adhesive resin may be used. Typical adhesive resins are polystyrene, styrene-butad-iene, polyethylene, polyvinylacetate, polyterpenes such as those made from pinenes, chlorinated rubber, tall oil rosin, and mixtures thereof.

The silicone gum used in the formula is a clear viscous dimethylpolysiloxane gum with a plasticity number ranging from to 120, as measured with the Williams plasticity number test, ASTM, -D-926, room temperature for 3 minutes. It should be noted that the incompatibility between the silicone gum and the other materials in the binder, i.e., waxes and resin, is a key factor in achieving the desired rheological properties mentioned above. Any suitable polysiloxane having a viscosity greater than about 30,000 centistokes may be employed whether it is a highly viscous liquid or a solid. Typical polysiloxanes include dimethyl, methyl vinyl, methyl phony], etc. of various molecular weights.

Using the preferred ingredients the process for making the above ink formulation is accomplished in the following manner. First, silicone gum is dissolved in xylene. The dyes are then melted together with the waxes and resin by heating them to about 250 F. for approximately twenty minutes. The solution of silicone gum is added to the foregoing melted mass and ground in a ball mill for about one hour. The dry pigments are mixed in a roller mill for about one hour and the resulting mixture is added to the foregoing mixture and milled until the pigment is well wetted. By first dissolving the silicone gum and then adding it to the molten mass of waxes, dyes, and resin, it is possible to maintain a workable mixture of the incompatible materials. Also, by delaying the wetting of the pigment materials and adding the finest pigments first, the possibility of grinding these materials to too fine and uniform a size is minimized.

The ink formulation is then coated onto a substrate or ribbon with a wire wound rod after which the xylene is driven off by heat. Suitable coatings range from 2.4-11 lbs/ream in which 500 sheets (20" x 30") make up a ream. Suitable substrates for the ink are Mylar (polyethylene terephthalate), paper, polyethylene, polypropylene, Nylon 66 (hexamethylene adipamide), cellulose acetate, Teflon (polytetrafluoroethylene), cellophane, rubber sheeting, tissue paper and typewriter ribbon paper. Good results have been obtained with a substrate thickness varying from .25 to 1 mil.

In addition to the above components listed, other materials may be added to the ink which will modify, synergize or otherwise enhance the performance of the ink.

Although the ink of this invention has been designed primarily for use in the specific duplicating technique described supra its good properties recommend it for other uses involving transfer imaging.

IEXAMPLES 1 1v An ink formulation containing microcrystalline wax, dyes, carbon blacks, toners, and oil is prepared and coated onto Mylar at a thickness of 7 lbs/ream. A typical formulation is as follows:

A suitable inked strip is placed into an automatic typewriter and typed onto bond paper. After removal from the typewriter, the original image is partially transferred to a sheet of commercial wax paper (Freshrap) by insertion between steel rollers at a pressure of 200 lbs. per lineal inch. The transfer sheet is then used for making copies in the same pressure device. This ink formulation gives a dense original, a somewhat fuzzy transfer sheet, and about 3 to 5 legible, but less dense, copies with a drastic drop in density after the third copy.

Three more tests are run in the same manner as Example I but with modifications in the ink formulation including the use of (2) a harder microcrystalline wax, (3) carnauba wax and (4) increased amounts of carbon black. Formulations 2-4 did not show any significant improvements over the ink formulation used in Example I.

EXAMPLE V An ink formulation is made with iron oxide in the pigment as follows:

Ingredients: Parts by weight Carnauba wax 16.0 Sunray DX (paraflin) 4.0 Armid HT (percent by weight-hexadecane 25,

octadecane 70, octadecane 5) 2 8 Victoria Blue BOC 1.8 Diethylene glycol 2.4 Arcturus oil 24.0 IRN 361 (iron oxide) 49.0

Copies produced in the manner described in Example I are very fuzzy and illegible after about the fourth copy. Also, it is noted that there is a tendency for the copies to smudge easily.

EXAMPLE VI The same test is made with an ink formulation that has the same ingredients as are used in Example VI except three high viscosity dimethyl polysiloxane oils (viscosi-ties 30,000, 60,000 and 100,000 centistokes) are substituted for the silicone gum, in Examples VII-IX, while a methyl vinyl polysiloxane and a methyl phenyl polysiloxane are used in Examples X and XI. Almost as many copies are produced in all instances as in Example V1 with only a slight decrease in density. There is also seen to be an increase in smudging as the viscosity of the oils decreases.

6 EXAMPLE VIH The same test is made with an ink formulation having the same ingredients as are used in Example VI, but omtting the silicone gum. Only 1 or 2 copies are produced with this ink formulation.

EXAMPLE IX The same test is made using the same formulation as that of Example VI but substituting ink oil 991 for the silicone gum. There is no significant improvement over the ink formulation used in Example I.

Other modifications and ramifications will readily become apparent to one skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of the present invention.

What is claimed is:

1. A pressure transfer ink comprising from about 33 to about 72 parts by weight of pigment dispersed in a binder, said binder comprising from about 3 to about 11 parts by weight of wax, from about 3 to about 10 parts by weight of an adhesive resin selected from the group consisting of polystyrene, styrene-butadiene, polyethylene, polyvinylacetate, poly-terpenes, chlorinated rubber, tall oil rosin, and mixtures thereof and from 25 to about 50 parts by weight of a high molecular weight polysiloxane having a viscosity of about at least 30,000 centistokes which is incompatible with said wax and said adhesive resin.

2. A pressure transfer ink according to claim 1 in which said polysiloxane is a gum.

3. A pressure transfer ink according to claim 1 in which said polysiloxane is a high viscosity oil.

4. A pressure transfer ink according to claim 1 further including from about 1 to about 10 parts by weight of dye which is soluble in at least one component of said binder.

5. A pressure transfer ink according to claim 1 in which said wax includes at least one member selected from the group consisting of polyethylene wax, paraffin wax, microcrystalline wax and beeswax.

6. A pressure transfer ink comprising from about 33 to about 72 parts by weight of pigment dispersed in a binder, said binder comprising from about 25 to about 50 parts by weight of a polysiloxane gum, from about 3 to about 10 parts by weight of an adhesive resin, from about 1 to about 4 parts by weight of beeswax, from about 2 to about 7 parts by weight of microcrystalline wax, and from about 1 to about 10 parts by weight of at least one wax soluble dye.

7. A method of making a transfer ink comprising dissolving from about 25 to about 50 parts by weight of a polysiloxane in an organic solvent, blending a hot melt of from about 3 to about 10 parts by weight of an adhesive thermoplastic resin, from about 1 to about 4 parts by weight of beeswax and from about 2 to about 7 parts by weight of a microcrystalline wax with from about 1 to about 10 parts by weight of wax soluble dye, combining said polysiloxane solution with said hot melt and blending the two together and adding from about 33 to about 72 parts by weight of pigment thereto and mixing until the pigment is well wetted therein.

8. A pressure transfer ink comprising from about 15 to about 40 parts by weight of iron oxide, from about 15 to about 25 parts by weight of carbon black, from about 3 to about 7 parts by weight of coal fines, from about 2 to about 10 parts by weight of wax soluble dye, from about 2 to about 7 parts by weight of microcrystalline wax, from about 1 to about 4 parts by weight of beeswax, from about 3 to about 10' parts by weight polystyrene, and from about 25 to about 50 parts by weight of polysiloxane.

9. A pressure transfer ink comprising about 26 parts by weight of iron oxide, about 21 parts by weight of carbon black, about 5 parts by weight of coal fines, about 10 parts by weight of wax soluble dye, about 5 parts by 3,262,806 7/1966 Gourge 106-31 X weight of microcrystalline wax, about 2 parts by weight of beeswax, 'about 8 parts by weight of polystyrene, and 2,519,321 3 1950 Newman 105.31 about 30 parts by weight of polysiloxane. 55 7 12/1958 Hart 0 References Cited 5 JAMES A. SEIDLECK, Primary Examiner. UNITED STATES PATENTS J. B. EVANS, Assistant Examiner.

3,016,308 1/1962 Macaulay 106-31 X