US2729575A - Method of making same - Google Patents

Description

D. A. NEWMAN 2,729,575

'PRESSURE SENSITIVE TRANSFER SHEET AND METHOD OF MAKING SAME Jan. 3, 1956 Filed Nov. 9, 1948 Snnentor DcfyZao' A. Nen/maw Eg Y Clttor'negs United States Patent() PRESSURE SENSITIVE TRANSFER SHEET AND METHOD OF MAKlNG SAME Douglas A. Newman, Sea Cliff, N. Y., assigner to Columbia Ribbon and Carbon Manufacturing Company, Ine., Glen Cove, N. Y., a corporation of New York t Application November 9, 1948, Serial No. 59,120

4 Claims. (Cl. 117-36) directed implement or by the type bars of a typewriter.

Transfer sheets of this type normally carry thereon a coating generally referred to pressure sensitive wax-carbon transfer material, the character of which depends upon the use to which the sheet is to be put. In the production of duplicate copies by direct pressure, such a sheet is usually referred to as carbon paper, the coating of which carries a dark pigment and leaves a mark onan underlying sheet when pressure is applied. Where a soluble dye is substituted for the pigment the sheet'may be used in the making of a master for hectograph reproduction, and Where the coating is primarily of ink-receptive material, with or without pigment, it is adapted for the production of plates or masters for use in a planographic printing process.

The character of the coating, in order to transfer properly when desired, is unfortunately soft and adhesive enough to be quite readily rubbed off in part by accidental and undesired Contact therewith. The use of transfer sheets of this character thus normally requires that the operator take particular pains to avoid smudging the coatings during handling, since, in the lirst two instances, pigment and dye material is readily transferred to the hands or clothing of the operator, or to` other surfaces Where it is extremely objectionable, and in all cases, rough or careless handling can result in serious defacement of the copies produced by causing an accidental and improper deposit of the transfer material on thebackground of the copy or master sheet.

Accordingly, my invention has for its object the production cfa transfer sheet of improved character such that the material o-f the transfer coating is readily transferable in the intended manner in response to concentrated local pressure, but will not be `retrieved `by the `ordinary frictional engagement attendant upon normal handling of the sheet. j p

While it has been known to coat transfer sheets for the purpose of making them smudge resistant, such operations have beenof questionable effectiveness due primarily to the surface characteristics of the coating materials used. It has been known,` for example, `that a coatingessentially of a wax or resin will offer some slight protection against inadvertent smudging` of the transfer material. As a practical matter, however, the results obtained with such a coating have not been found to be acceptable. The reason for this is that a light coating of the material is readily displaced `by scuting or abrasion with a concurrent disruption lof the underlying transfer material, while a coating heavy enough to be truly described as abrasion-resistant becomes a substantial impediment to transfer in the usual and intended manner. It is another object of my` invention, therefore, to provide a `transfer sheet having a protective coating of `such character that it can be applied in a` layer suiciently thin to avoid interference with normal` transfer,

and having covering and surface properties such that the same is in fact resistant to inadvertent smudging and abrasion.

In particular I have found that abrasion of the known resin protective coatings is apparently due primarily to the fact that such materials have a surface which is characterized by minute projections imparting to the same frictional characteristics which result in a pronounced tendency for the coating to cling to and be displaced by objects having sliding or rubbing contact therewith. In accordance with my invention I obviate this difficulty by providing as an ingredient of my coating composition, an anti-friction shielding component preferably in the nature of lamelliform particles; While the exact operation of this component is not at present entirely known, the same appears to provide sufficiently high percentage of flat, smooth areas on the coating surface to markedly reduce its friction properties and, in the same degree, reduce the tendency towards abrasion and scufling. It is further thought that the tendency of the lamellae to assume overlapping positions largely increases the covering power of a coating of a given thickness by reducing the number of innitesmal imperfections often occurring in thin coats, with the result that seepage of transfer material through the coating is largely precluded. Sutlice it to say, however, that by using the anti-friction shielding component in the coating of my invention, it has been found possible to use coatings well Within the degree of thickness which is suitable for proper normal transfer action, and which are still proof against abrasion` to such a degree that substantially normal transfer pressure must accompany the same in order to register any material derangement of the surface.

l have further found that this incorporation of lamelliform particles in the coating composition simultaneously provides a distinctive appearance to the surface coated, with the result that a great saving of the operators time is effected. This saving derives from the fact that sheets having my improved coating are readily discernible so that the operator can determine at a glance which sheets or portions thereof have been protected against smudging and can handle the same in a rapid and unmeticulous` manner, even in the case when the same are mixed with unprotected or inferiorly protected sheets.

Further objects and advantages will hereinafter appear. In the drawing:

Figure l is a fragmentary section of a transfer sheet provided with a protective layer and illustrating the principle of my invention.

Fig. 2 is a view similar to Fig. 1 illustrating the prep master unit in accordance with my invention.

The transfer sheet of my invention is illustrated broadly in Fig. l wherein is shown a base 11 of tissue paper or like material provided with a coating 12 of transfer material. The coating 12 normally comprises a wax base and suitable plasticizing and hardening ingredients. if the sheet is to be used for the making of direct copies, the coating` 12 also contains a pigment and the sheet is then known as carbon paper. When, instead of pigment, the coat contains a soluble dye such as crystal violet, the sheet may be used in the making of hectograph masters. With a wax coating of suitable properties, with or without a pigment, the sheet may be used to transfer an inkreceptive image to the surface of a planographic sheet. In any case, the coating 12 is subject to smudging by the t hands of the operator and to unintentional transfer if care werenot used in placing the same against the copy sheet or master. To protect itagainst such smudging the coating 12 is covered by a coating 13 which makes the sheet resistant to casual smudging and Apermits transfer only when desired in response to usual transfer pressures.v The Vcoating-13 is tough enough to cling together during normal handling. Furthermore, the coating 13 should be relatively friable and adhesive so that proper local transfer will occur in response to pressure when desired.

will vinclude a resin soluble in one of the solvents mentioned above, and an oleous 'or waxy ingredient which has the effect of ameliorating ythe toughness of the resin an'dthus rendering the coating somewhat more friable.V

'While coatings las described above have been attempted as protective coatingsfor transfer sheets, their effectiveness has'proved to be extremely limited, since the provision of athin coating suitable for proper yfunctioning of the'sheet inits transfer capacity are readily abraded and scuffed Vby'incidental contact with the surface, and

coatings'thick enough 'to substantially avoid the latter diculty are found to seriously impair the transfer operation for which the sheet is intended.

My improved coating 13 includes as an ingredient :thereof an anti-friction shielding vcomponent preferably consisting of Vminute lamelliform particles 14. The composition ofthe particles is not important, and any material which can beproduced in a finely divided Vstate with the desired lamellar form and which is unaffected by other ingredients of the coating is suitable. I have found, for example, that certain materials known in the art of pigments as bronze powders, are especially suited for the present purposes. The term bronze powders as used in this connection yrefers to flaky powders of varying metallic composition, including, for example, Valuminum as well as those of copper alloys known asbronze (inthe metallurgical sense). It has also been found that graphite powder can be prepared having a aky nature suitable to the present purposes, and that groun'dfsh scales and mica also have this character.

While various binders, plasticizers, solvents vand antifriction shielding components may be employed in'varying proportions in producing my improved vcoating as i indicated above, the following illustrates one form of coating composition which l'have found to be particularly suitable and which gives an indication of the relaltive 'proportions -of the Vvarious ingredients required in making up such a coating: K

One method which I have used in the application of coatings such Vas 13 with very desirable results, consists in first 'spreading the coating material 13, carrying particles 14, in a thin layer and allowing the same to` set, as by evaporation of ythe solvent if any. Then an aftertreatrnent is resorted tov .in which .a butiing wheel .is lightly appliedto the exposed surface of the coating 13. lThis has the effectof polishing the sameand rendering iteven more markedly resistant to abrasion and smudging, ap-

4 parently due to the rearrangement of the particles 14, or a portion of them at the surface of layer 13, parallel to the plane of the base 11.

While the preferred form of the coating 13 as described above contains a solvent applied binder including a resinous ingredient, my invention is not to be considered as limited in this respect and may employ binders of resins or waxes applied in various ways. For example, it has been known to provide an overcoating of wax on transfer sheets in anreffort to protect the same against smudging. The application of such a coating is rendered somewhat complicated by reason of the fact that the pigment Vor dye layer of the sheet is usually a wax-base material and Vadditional factors are thus introduced into the coating problem in order to prevent commingling of the coatings.

it is possible, however, by spraying orv brushing on thev wax overcoat in a semi-liquid state, or by arranging the waxy constituents of the two layers so that the overcoating has a lower melting point than the pigment layer, to provide such a wax coating on the surface of the transfer sheet. This protective layer ofY wax, when applied, is subject to objection similarly to other protective coating materials in that the same is rather soft and is almost instantly abraded off or brushed aside by normal handling and use when laid onrin a thin layer capable of transferring readily and accurately. Likewise, when a heavy layer which is eifectivelyprotective is used, the excessive thickness of wax which must be transferred, seriously affects theV reliability with which the coatings can be separated'from the backing sheet and thus prevents the transfer image from being entirely sharp and clear. The addition of the anti-friction shielding component 14.to such a coating where the binder is merely one of wax has an equivalent elfect in this instance, making it possible to lay a protective coating which is suicientlythin to transfer properly and which at the same time atords adequate protection.

The effect of such an anti-friction shielding component 14 is greatly to increase the covering power of the coating so that less of the binder need be applied to a given area, with the result that a coating which is thoroughly effective against incidental abrasion smudges and which is furthermore readily transferable in the desired locality, is deposited. The shielding effect of the anti-friction comV ponent is 'greater than can be predicted on the basis of the proportions used. While thereason for this result is not entirely known at present, the flaky character of the component 14 appears to be the feature which gives rise to this new result and it is assumed that the slight overlapping of the flakes provides alamellar armor which is capable of turning aside the ordinary manual contact, and which further presents Va surface with substantially reducedv frictional characteristics. With a shielding component of this character incorporated` in the coating 13 it is found `that the covering and shielding etfected is increased in such a way that much less of the binder is required; thusrvthe coating has improved friability and its transfer property is markedly superior to that of a coating lacking this ingredient when applied in a layer thickenough to give the appropriate minimum protection against smudging. s, y

"The addition of the particles 14 also performs the rimportant function of giving a distinct appearance to the sur# face coated. When the particles 14 are included, the surface'takes on a distinctive sheen, and has aicolor corref sponding to the material chosen. Thus, when auser is employing transfer sheets of various types, only some of which are provided with effective protective coatings according to my invention, he is at oncervisually informed as to whether' any particular sheet is suitably protected or not,

and cangovern his handling thereof accordingly. Likewise, where the protective coating extends over a lpart .only of the sheet, the ,user can determine ata glance thevportionsof the sheet `which are intended for manual engageprotective layer, as shown in Fig. 2, is the preferred form of my invention. In this case the base sheet 11 has a coating 12 of transfer material thereon. The coating 12 is protected by means of a layer 13a. This layer is formed by first applying a coating 13b containing resinous material such as Tornesit applied by means of a suitable solvent and which may have suspended therein the lamelliform particles 14. This coating may, for example, be composed similarly to the coating 13 described above. A surface coating 13e consisting primarily of wax is then applied over the coating 13b. This can be very readily accomplished by melting the coating material and applying the same with a` heatedroller, although other application methods may also be used if desired. It has been found that with such a composite layer, the thickness of the coating 13b can be reduced since it in turn receives some protection from the wax coat. While the wax itself offers only partial resistance to scuffing or abrasion, the underlying coating 13b including flaky particles will form a mechanical barrier which inhibits penetration of an abrasive attack to the surface of the transfer coating 12. The protective effect of the layer 13a is also due in part, apparently, to the diverting eect of the additional surfaces between the coatings 13b and 13C. In fact, the combined thicknesses of coatings 13b and 13e; i. e. the overall thickness of the protective layer 13a, because of the increased shielding properties demonstrated, can be held within the same fully acceptable thickness range for proper transfer that is an important feature of the coating 13 previously described. It is found as a practical matter that the wax provided by the coating 13c is the material which responds most favorably to controlling devices used in the ordinary paper coating equipment with the result that a more uniformly surfaced and more generally desirable product results. The solvent applied coating 13b at the same time provides a barrier against commingling of the wax coatings 12 and 13o whereby the latter may be applied in the most expeditious manner without resorting to the unusual and expensive coating procedures which would be necessary if a protective coating of melted wax were to be applied directly to a transfer coating having a wax base.

Fig. 3 illustrates a preferred form in which the protective layers of my invention may be applied, the transfer sheet as a whole being designated by the reference character and comprising a base sheet 11 of tissue paper or the like having thereon a coating 12 of transfer material. A protective layer 15, constituted in accordance with the description of the coating 13 or layer 13a described above, covers the surface of the coating 12 and also preferably extends so as to embrace and cover the edges of the coating 12 as indicated by reference character 16. Since transfer sheets are often necessarily manipulated by their edges,

the portions 16 of layer 15 are important in preventing traces of the dye or pigment from migrating to the hands of the user in which case itis difficult if not impossible to keep the copies or masters clean.

One important application of my invention relates to the construction of composite units known as master units, and particularly to the preparation and use of the same in continuous form. Such a unit is shown at 2t) in Fig. 4 and consists of a master sheet 21 and a hectographic transfer sheet 22 detachably connected thereto along one margin and having a hectographic transfer surface 23 on the upper face thereof. The sheet 21 is designed to receive written or typed inscriptions on its upper surface, the same being reproduced in reverse on theunder surface by virtue of t the juxtaposedtransfer surface 23. After removal of the sheet 22, the image `on the under surface of sheet 21 is capable of being used as a spirit process master for direct engagement with a number of copy sheets, the inscription thereon being suitably moistened from time to time with a solvent for the hectograph dye now carried by that surface. The inscriptionon the upper surface serves merely to indicate, in a direct-reading fashion, the character of the hectographic image on the lower surface.`

It is frequently desirable to provide units such as 2G with pre-printed inscriptions, such as forms and headings 24 which will reproduce hectographically along with the additional typed or Written material. In order to accomplish this, the unit is passed through :a printing machine and inscribed with the pre-print 24 which results in the reverse-reading hectographic impression 25. If such a unit of the ordinary type has been in storage, it will have i hada slip sheet placed between the unit sheets to prevent accidental transfer and incidental migration of the dye from sheet 22 to the under surface of sheet 21. This slip sheet must be removed before printing, replaced after printing, and again removed by the user before Writing or typing. A further replacement and removal of the slip sheet may be required if any substantial storage or handling period intervenes between the nal inscription and the production of copies. The slip sheeting procedure thus becomes extremely complicated and unwieldy and is especially undesirable where the units are being used in continuous form by semi-automatic machinery in an effort to minimize the time spent in producing such masters.

According to my invention, the hectographic transfer surface 23 of sheet 22 includes a protective layer having the characteristics described above for the layer 13 or 13a, and the same has been found to prevent accidental smudging to such a degree that acceptable copies result when the use of slip sheets is dispensed with entirely. Thus a tremendous saving in time, expense and annoyance is realized.

Fig. 5 illustrates a master unit 30 somewhat similar to that shown in Fig. 3 out intended rather for planographic work. Here a transfer sheet 31 has a surface 32 on the under face thereof, consisting in part of transferable ink-retaining material in the nature of Wax which may also contain a pigment if desired. Detachably connected to the sheet 31 is a sheet 33 having an upper planographic surface 34. This unit 30 may be inscribed by printing, writing or typing on the upper surface of sheet 3l with the concurrent production of an ink-retaining direct-reading image on the planographic surface 34 of sheet 33. Pre-printed forms and headings 35 may be used in the same manner as explained in connection with the unit 29 of Fig. 3, producing, however, a direct-reading ink-receptive image 36. When the transfer sheet 31 has been removed, sheet 33 is used as the printing member or plate in an offset planographic reproduction process. If a direct printing is desired in place of the usual offset, the inscription of the unit 30 is effected on the lower side of planographic sheet 33 instead of on sheet 3l. In any event when the transfer .surface 32 s prepared so as to include a protective layer in accordance with the description of layers 13 or 13a' above, it is found to be sumciently resistant of itself to incidental smudging and abrasion during handling and storage, with the result that the costiy and time-consuming use of slip sheets is entirely avoided and savings effected in the same manner and to the same degree as described for the hectographic unit of Fig. 3.

Variations and modifications may be used within the scope of this invention and portions of the improvements may be used without others.

I claim:

l. The method of making a pressure sensitive transfer element which includes the steps of applying to a base having a pressure sensitive wax-carbon transfer coating thereon including a soluble dye, a first coating on said transfer coating comprising a major portion of a resinous film-forming substance and a solvent therefor which is a non-solvent for said dye; drying said coating by evaporating said solvent; applying a second coating on said first coating comprising a major portion. of wax in molten form; and hardening said second coating by cooling the same.

2. The method of making a pressure sensitive transfer elementwhich includes the steps of-applying toa base having `a pressure sensitive wax-carbon transfer coating thereon, a girst coating onsaid transfer coating comprising a' resinous film-forming substance, insoluble lamellform particles and a solvent for the film-forming substance which is not a solvent for said transfer coating, drying said coating by evaporating the solvent; applying a second coating comprising a major portion of molten Wax;` and hardening the second coating by cooling the same.

,3.V A pressure-sensitive transfer member comprising a flexible base sheet; a transferlayer of pressure-sensitive, image-reproducing material` including a Wax bindet` and soluble color-bearing material suspended therein on asurfaceof said base sheet; a rupturable protective layer superimposed on the transfer layer, said protective layer including va thin, rupturable layer consisting of the resi- Vdue of'a coating solution including a resin and a volatile. solventfor the resin adhered to the surface of the transfer layer; and a surface coating comprising a major portion of wax superimposed on the resinous coating.

4. A pressure-sensitive transfer member comprising a ilexible base sheet; a transfer layer of pressure-sensitive,

image-reproducing.,material including a wax binder and soluble vcolor-bearing Amaterial Asuspended `therein on a surface-ofsaid base sheet; a rupturable protective- -layer superimposed on the transfer layer, said protective layer includingar-thin,-rupturable layer adhered tothe surface of the transfer `layer consisting of the residue of Ya coating solutionincluding a resin, a volatile solvent for the resin, and insoluble lamelliform particles suspended therein; and a-surface coating comprising a major portion of wax superimposed on the resinous coating.

References Cited 4in the file of thisl patent UNITED STATES PATENTS 997,125 Gleason A- July 4, 1911 1,315,311 Kirkbrilde Sept.,9, 1,919 1,864,097 Sherman June ,21, 193,2 1,971,306 Antrim' v Augjzl, 1934V 2,069,648 Denner Feb. 2, V1937 2,188,590 Bjorksten Jan. v30,1940 2,306,046 Duggan Dee.V `22,1942 2,362,884 Clark Nov. ,14, 194,4 2,398,779 Dalton Apr. 23, 1946 Y 2,671,734

Rosenblurn Mar. 9, .1954

Claims (1)

1. THE METHOD OF MAKING A PRESSURE SENSITIVE TRANSFER ELEMENT WHICH INCLUDES THE STEPS OF APPLYING TO A BASE HAVING A PRESSURE SENSITIVE WAX-CARBON TRANSFER COATING THEREON INCLUDING A SOLUBLE DYE, A FIRST COATING ON SAID TRANSFER COATING COMPRISING A MAJOR PORTION OF A RESINOUS FILM-FORMING SUBSTANCE AND A SOLVENT THEREFOR WHICH IS A NON-SOLVENT FOR SAID DYE; DRYING SAID COATING BY EVAPORATING SAID SOLVENT; APPLYING A SECOND COATING ON SAID FIRST COATING COMPRISING A MAJOR PORTION OF WAX IN MOLTEN FORM; AND HARDENING SAID SECOND COATING BY COOLING THE SAME.

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