US3054692A - Novel hectograph methods - Google Patents

Description

Sept. 18, 1962 D. A. NEWMAN ETAL 3,054,692

NOVEL HECTOGRAPH METHODS Filed NOV. l5, 1959 /S/o- MASTER v A 50M/+575? @me 2S w 7 I-TQANSF7 545.57'

50 -Mfgsek l 'lll/IL'. JQ?. 4 35 15 w /o-re/Q/VSFE/Q SHE-E7 INVENTORS Douglas A. Newman gYZdn Sdoz/vezu er' HTToE/VE Y6 United States Patent O 3,054,692 NOVEL HECTOGH METHODS Douglas A. Newman, Glen Cove, and Allan T. Schlotzhauer, Locust Valley, N.Y., assignors to Columbia Ribbon and Carbon Manufacturing Co., Inc., Glen Cove, N.Y., a corporation of New York Filed Nov. 13, 1959, Ser. No. 852,612 6 Claims. (Cl. 117-175) This invention relates to improvements in the thermographic and xerographic methods of imaging hectograph master sheets, and more particularly to the use of novel heat-resistant hectograph transfer sheets in such methods.

It is known to prepare transfer sheets which carry a pressure-transferable layer of wax and color forming material and such sheets are the most common in use today. When a master sheet is placed over these sheets and pressure is applied, the said hectograph layer, corresponding to the pressured areas, transfers to the master sheet. In the spirit duplication process, many copies can be made from the prepared master sheet.

However, these hectograph transfer sheets have certain disadvantages. Of prime importance is the fact that a wax binder is not soluble in the fluids used to make spirit hectograph copies and further that the wax has a certain miscibility with modifying oils used in preparing the hectograph formulations. In other words, in a typical formula, approximately l to 15 parts of carnauba or other relatively high melting point vegetable waxes together with approximately l() to l parts lanolin and l0 to l5 parts mineral oil are melted together. Naturally it is understood that other modifying agents such as castor oil, paraffin wax, butyl stearate, etc. can be included or replace totally or in part the mineral oil and/or lanolin but the facts are that in general about one part of wax is used to two parts of modifying ingredients. In this event, the wax has miscibility with these materials so that the formula actually becomes more or less unified, all of which is not miscible with alcohol save perhaps those modifying agents such as butyl stearate or lard oil, castor oil, etc. that might be included, but in any case the wax base formula itself exhibits incompatibility with alcohol.

In using such a formula to prepare a hectograph ink, approximately one part of formula to two parts of dye are ground together and coated hot on the paper which on cooling solidies, making a transfer lm as originally described. In use, of course, the master having the hectograph formulation in image form is pressed against paper carrying a solubilizing fluid, principally alcohol, and as copies are produced the dye is leached out of the master. As the run continues, the ratio of dye to bonding agent reduces, particularly at the interface, until finally so little dye is taken off per copy that the copies are no longer acceptable. However, there is a great deal of dye remaining on the master that never is spent or dissolved away because the Wax forms a protective layer over the dye and only that amount of the color forming material which is present at or relatively near the surface of the wax image on the master sheet can be reached by the duplicating lluid and transferred to copy sheets. Thus the number of copies that can be derived is limited to the amount of dye that can be leached out in the above described manner. In short, the disadvantage with the known hectograph sheets is the fact that they contain only a limited amount of material which transfers to and stains the copy sheets. Thus a relatively large percentage of the image on the master sheet constitutes wax binding material which remains behind on the expired master sheet and is wasted for imaging purposes.

Another serious disadvantage of the conventional hot melt wax hectograph transfer sheets is the fact that they 3,054,692 Patented Sept. 18, 1962 ice are meltable at temperatures in the range of F. and above and therefore give rise to many problems when used in heat processes such as thermography and xerography. Attempts to use these conventional hectograph transfer sheets in heat processes have failed since the wax coatings melt at the prevailing temperatures which range between 15T-450 F. and completely block off to the master sheet giving rise to a blurred master sheet and unrecognizable copies. In short, the transfer layer is transferred completely lto the master sheet and no definite imaging occurs.

Therefore it is an object of the present invention to prepare hectograph transfer sheets which have none of the aforementioned disadvantages, and which provide for the preparation of sharper, more clear and more numerous copies through the spirit duplicating process than heretofore possible.

It is another object of the present invention to prepare spirit hectograph transfer sheets in which substantially all of the color forming material or dye is available for producing copies.

It is a further object of the present invention to prepare spirit hectograph transfer sheets in which the binding material does not interfere with the availability of the color forming material or dye for the imaging of copy sheets, and which is not wasted on the expired master sheet.

However it is the main object of the present invention to prepare hectograph transfer sheets which are heat stable and which do not melt at the temperatures required by the thermographic and xerographic processes.

These and other objects are accomplished in the manner disclosed hereinafter.

In the drawings:

lFIGURE 1 is a diagrammatic cross-section, to an enlarged scale, of a master sheet and a hectograph transfer sheet having on the transfer layer xerographically-applied images superposed under the influence of heat but separated for purposes of illustration.

FIG. 2 shows the master sheet and hectograph transfer sheet of FIG. 3 after heating and separation.

FIG. 3 is a diagrammatic cross-section, to an enlarged scale, of a master sheet, a hectograph transfer sheet and an imaged original sheet superposed under the influence of infrared radiation in the thermographic process but separated for purposes of illustration.

FIG. 4 shows the master sheet and the hectograph transfer sheet of FIG. l after irradiation and separation.

According to the present invention, instead of wax as the binder, a cellulosic film-forming material such `as ethyl cellulose is used which is at least partially soluble in the spirit duplicating iluids. Further, while the formulation contains oils, lanolin or other modifying agents in similar proportions to the wax base type, if they do become bonded with the ethyl cellulose they will transfer with the dye on copying since the ethyl cellulose is alcohol soluble. This situation also permits `almost total exhaustion of the dye from the master, producing many more copies. It must be realized that formulations can be modified for copy brilliancy depending on the proportions of the nonvolatile, non-miscible component to the bonding agent, that is to say, by changing either non-volatile component, cellulose or the dye proportions. Some dyes are much more soluble than others but in the last analysis the sealing properties of wax as against ethyl cellulose are such that the former seals While the latter more completely solvates thereby making available more dye from an impressed master sheet.

An equally important reason for the superior results obtained by plastic bonded type coatings is thought to be that since the coating in the case of the cellulose bonded hectograph is applied with solvent and contains nonvolatile, non-miscible materials, the cast film on drying is relatively porous having minute micellular structure, permitting alcohol to penetrate through the transferred image and in this way bringing about more complete solvation. Wax of course is insoluble in alcohol and prevents the penetration thereof.

When it is considered that each dye particle is surrounded by the vehicle in either case and when it is considered in the case of the cellulose film-forming material that the dye particles are surrounded by alcohol wettable resin, then it can be understood that dye solvation is more complete. Also the wettability of the dye by alcohol is improved over Wax bonded formulas and exhaustion of the master takes place more completely.

While the above advantages (in respect to solvent resin bonded style of transfer coatings) are important from the standpoint of straight spirit hectograph duplication, the most important advantage from the standpoint of this invention is the heat resistance of the present transfer sheets.

There are at present two principal methods for accomplishing this which are applicable to forming hecto masters. One is Xerography and the other, thermographic means involving infrared radiation.

In the first case, as illustrated by FIGS. l and 2 of the drawing, a Xerographic image may be formed on the face 11 of the solvent type of hectograph sheet lit and that sheet together with a master 3d under suiiicient pressure to hold the two rmlly together subjected to heat 50 in which action the xerographic resin powder is fused in the imaged area so that the master and hectograph layer are Welded together at said imaged areas. On separation after cooling, the dye layer is removed at said imaged areas and a master is thus prepared having the Xerographic image 15 and a portion 3'5 of hectograph transfer layer adhered thereto.

The second consideration, that is to say thermographic means, as illustrated by FIGS. 3 and 4 of the drawing, the solvent type hectograph layer 11 may be cast on a more or less translucent base sheet 10 or a sheet at least which allows the penertation of infrared radiation. The said coated sheet together with a master 30 plus the copy sheet having original images 21 thereon to be copied are fed through a thermographic machine having infrared radiation 50 in which act heat is developed in the image areas of the original, thereby causing a softening of the layer and welding the master in said areas to the hectograph sheet which on cooling and separation affords a mirror reverse facsimile image 31 on the master.

=Now to further improve upon the Welding of the master to the hectograph layer, it may be advisable to either hlm over the hectograph layer or apply a lm to the master, said tilm having particular ajhnity for the master onl the one hand or the hectograph layer on the other, as the case may be, when, hot, thereby effecting a better, more complete transfer after cooling and separation. The Whole pointis that these solvent resin bonded type coatings, while they might soften with heat, do not ow out as does a Wax coated sheet. Naturally it should be understood that `a coating that becomes liquid under these temperatures is inoperable in the case of xerography 'to form a master as described because the whole hectograph mass would block off and adhere to the said master. Similarly, in the case of the thermographic method, the criticality would be much greater when flowable ink is used because of ambient temperature developed in the machine, whereas with a hectograph coating that does notr become molten or fluid but merely softens, the criticality of the temperature factor is greatly reduced. Natura'lly, various modifications can be made in the composition of the resin bonded layer and/ or undercoatings or supercoatings to fit an intended use, all of which will be well known in the art. The fact is that besides having a Y volatile solvent, or by applying such coating in the form of an organosol or pflastisol in a manner well known to the art. The preferred method, however, is the solvent application.

After application of the coating, the solvent is evaporated and there results the formation of a hectograph layer which does not melt at elevated temperatures but becomes soft but not flowable at temperatures between 15045Q lF., which are the temperatures used in the thermographic and Xerographic processes.

Example I The following ingredients were thoroughly intermixed to a coatable consistency:

Parts by weight Lard oil 8 Oleic acid 8 Filler (if desired-may be graphite or carbon black) 4 Hectograph dye (Du Pont Spirit Black #3) 20 Ethyl cellulose 5 Solvent (toluol or the like) 55 The mixture was then spread evenly on a suitable base, such as paper, by suitable coating apparatus and allowed to cool and to set by evaporation of the solvent to form a smooth, pressure-transferable and heat-transferable hectograph coating having the properties described.

The prepared transfer sheet was then compared 'with a conventional hot melt Wax hectograph sheet in the following manner: Two original sheets which were desired to be copied were placed face-up; then the novel hectograph sheet of the present invention was placed faceup over the tirst original and the conventional hectograph sheet was placed face-up over the second original; next a suitable master sheet was placed over each of the transfer sheets, in contact with the hectograph layer, to form a pack. Each pack was then passed through a Thermo- Fax machine. The infrared radiation of the machine was focused on the master sheet and penetrated through to the original sheet where it was absorbed by the images on the original sheet and converted to heat in these areas. The heat generated by the images causes the overlying transfer sheet to heat up over the imaged areas thereby bonding the master to said imaged areas.

Upon emergence from the machine, both pac-ks were examined and tested. The pack carrying the conventional hectograph sheet Was found quite inferior for many reasons. It appeared that the imaging layer of the conventional hectograph sheet had melted and become fluid at the existing temperatures and blocked olf totally to the master sheet due to the overall ambient temperature of the thermographic machine and the lack of heat resistance of the transfer layer.

None of these defects was present in the pack containing the novel hectograph sheet of the present invention. It was found that the imaging layer of this sheet had not melted at the temperatures of the thermographic machine but merely became softened and adhesive over the image areas of the original sheet. The hectograph layer over these areas fused itself to the master sheet and transferred thereto in a substantially stenciling manner to give a sharp, clear master sheet having minimal background stains. Likewise it was found that the present transfer sheets permit for varying the density of the copies produced due to their heat resistance over a relatively wide temperature range. For instance, where denser copies and a longer running master sheet are desired, the speed at which the pack is run through the thermographic machine may be decreased thus allowing for increased heat formation in the imaged areas and a denser master sheet.

Each of the prepared master sheets was tested in a spirit duplicating machine and it was found that the novel sheets of the present invention resulted in cleaner, sharper and over 50% more numerous copies than the master sheet prepared from the conventional hectograph sheet.

Example Il The above ingredients were mixed to a coatable consistency and coated on a suitable foundation as in Example I to form a hectograph transfer sheet.

This transfer sheet was then placed in face-to-face contact with a selenium plate carrying an electrostatic powdered image under suicient pressure to keep the two elements in close contact. A corona discharge was applied, thereby reversing the polarity and upon removal of the hectograph sheet the powdered image adhered to the hectograph layer. The hectograph sheet bearing the powdered image was then placed in face-to-face contact with a master sheet to form a pack which Was placed in a xerox oven at temperatures between 400-4501 F. and the powdered image fused and picked on" the softened, non-fluid hectograph layer in the areas overlying the powdered images. Thus there was formed a master sheet, carrying a substantial amount of hectograph material in the electrostatic image areas, which may be used to prepare many sharp copies in the spirit process.

An attempt to employ conventional hot melt wax hectograph transfer sheets in this process failed due to the fact that the dye layer melted to a fluid state at the required temperatures and the uid transferred to the master sheet throughout.

The proportions shown in the examples are not to be considered critical, the important factor being that the binder material is soluble in the spirit duplicating uid. It has been found that amounts of binder as low as 2 or 3% based upon the total Weight of the transfer composition may be used with excellent results, and that the amount of hectograph dye may be as high as l times the weight of binder used. The heat-resistance of the present transfer sheets appears to be due to the heatresistance of the cellulosic resinous binder and the large amount of hectograph dye material employed.

No particular criticality exists with regard to the nature of the cellulosic binder so long as it is at least partly soluble and preferably completely soluble, in the spirit duplieating uids employed. The preferred binders are the cellulose ethers, particularly ethyl cellulose which is very soluble in ethyl alcohol and mixtures of ethyl alcohol and water, which are the most common duplicating fluids. Other cellulosic -binders which may be used include cellulose ethers such as methyl cellulose, carboxymethyl cellulose and others. It should be noted, however, that when the binder employed is water-soluble that the imaging material employed should be one which is not soluble in water. It is useful in some instances to overcoat the hectograph layer or coat the master sheet with a wax supercoating containing frangible, tacky material such as beeswax, Indopol and Vistanex to improve the attraction of the transfer layer from the master sheet.

It has been found that when the novel transfer sheets of the present invention are to be used in thermographic processes wherein the heat source is radiation such as infrared, then it is preferred that the master and transfer sheets be of such a nature as to allow the radiation to easily pass through. -In this regard, transparent, translucent and transpicuous sheets are Very satisfactory, such as clear plast-ic, frosted or crazed plastic, glassine paper, etc. Likewise the hectograph dye `layer should be permeable to infrared radiation and should not contain any materials which absorb infrared radiation to any substantial degree. Suitable infrared-permeable dyes include rhodamine dyes, malachite green, safranine dyes land the like.

It has also been found that substantially colorless colorformers may be used in place of the colored dye on the transfer sheets. Such compounds are infrared-permeable and produce a `bright color when lbrought in contact in the spirit process with complementary chemical reagents which are present on the treated copy sheets in the manner set forth in our copending application Serial No. 598,759, led .uly 19, 1956, and now abandoned. For example, a compound such as gallic acid, tannic acid, rubeanic acid, hematoxylin, sodium thiocyanate or any of the conventional color-formers as listed in the aforementioned application and in United States Patent No. 2,663,656 may be included in the ethyl cellulose layer in place of the hectograph dye. Copy sheets are prepared which are treated with complementary precipitant meta-l compounds such 'as those of iron, vanadium, copper, nickel, etc. as listed in the aforementioned application and patent. It is also possible to use substantially colorless unreacted dye components, one on the transfer sheet and the other on the copy sheets, which when brought together in the spirit process produce colored images.

One precaution must be observed, however, when using the aforementioned complementary color-forming compounds in thermographic processes of producing master sheets. When the transfer sheet and master sheet are heated together with the original to elect imaging of the master sheet, the temperature should be kept suiciently low to prevent decomposition of the color-forming chemical land to compensate for the lower temperature the period of heating should be extended.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be -used without others.

We claim:

l. In the thermographic process `of producing an imaged hectograph spirit master directly from original infrared radiation-absorbing images and a hectograph transfer sheet whereby the master, hectograph transfer sheet and the original images are superposed and infrared radiations are passed therethrough, the original images absorbing the same and converting them to heat, the improvement which comprises using as the hectograph transfer sheet one which does not absorb infrared radiation to any substantial degree and which carries a pressure-sensitive transfer layer which is based upon a cellulosic film-forming binder material containing a non-volatile component which is non-miscible with said binder material and which is selected from the group consisting of oleaginous and pasty compositions, and a quantity of spirit-soluble imaging material, and the transfer layer softens but is noniluid at temperatures between about F. and 450 F., the temperature of the theunographic process.

2. The process of claim l, wherein the hectograph transfer sheet comprises a flexible foundation having thereon a pressure-sensitive transfer layer comprising ethyl cellulose binder material which is at least partially soluble in the conventional spirit duplicating fluids, a mixture of lard oil and oleic acid `and a quantity of spiritsoluble imaging material.

3. The process of claim 1, wherein the hectograph transfer sheet comprises a ilexib'le foundation having thereon a pressure-sensitive transfer layer comprising ethyl cellulose binder material which is at least partially soluble in the conventional spirit duplicating ui'ds, a mixture of mineral oil and Ilanolin and a quantity of spiritsoluble imaging material.

4. In a Xerographic imaging process of producing lan imaged hectograph spirit master through the medium of a transfer sheet having a transfer layer thereon comprising hectograph imaging material, whereinan electrostatic image of electroscopic powder is `formed on the surface of a Xerographic plate, the electroscopic powder image is transferred so as to he positioned between the transfer layer on said transfer sheet and the surface of the master sheet and heat is applied to eitect fusion of the electroscopic powder image Iand the underlying transfer layer comprising said hectograph imaging material to the master sheet whereby said imaged hectograph spirit master is formed upon separation of the sheets, the improvement which comprises using as the transfer layer on the transfer sheet one which -is based upon a `cellulosic film-forming binder material containing a non-volatile component which is non-miscible with said hinder material `and which is selected from the group consisting of oleaginous and pasty lcompositions, and a quantity of spirit-soluble imaging material, said transfer layer being non-uid at temper- 8 atures between about 150 F. and 450 F., the temperature required for the heat transfer of the hectograph imaging material to the master sheet.

5. The process of claim 4', wherein the hectograph transfer sheet comprises a flexible foundation having thereon a pressure-sensitive ltransfer layer comprising ethyl cellulose lbinder material which is at least partially soluble in the conventional spirit duplicating iluids, a mixture of lard oil and `oleic `acid and a quantity of spiritsoluble imaging material.

6. The process of claim 4, wherein the hectograph transfer sheet comprises a flexible foundation having thereon a pressure-sensitive transfer layer comprising ethyl cellulose binder material which is at least partially soluble in the conventional spirit duplicating uids, a mixture of mineral oil and lanolin and a quantity of spirit-soluble imaging material.

References Cited in the file of this patent UNITED STATES PATENTS 2,616,961 Groak Nov. 4, 1952 2,808,777 Roshlrind Oct. `8, 1957 2,810,661 Newman et al Oct. 22, 1957 2,930,106 Wrotnowski Mar. 29, 1960 2,954,291 Clark Sept. 27, 1960 2,954,311 Vander Weel Sept. 27, 1960

Claims (1)

1. IN THE THERMOGRAPHIC PROCESS OF PRODUCING AN IMAGED HECTOGRAPH SPIRIT MASTER DIRECTLY FROM ORIGINAL INFRARED RADIATION-ABSORBING IMAGES AND A HECTOGRAPH TRANSFER SHEET WHEREBY THE MASTER, HECTOGRAPH TRANSFER SHEET AND THE ORIGINAL IMAGES ARE SUPERPOSED AND INFRARED RADIATIONS ARE PASSED THERETHROUGH, THE ORIGINAL IMAGES ABSORBING THE SAME AND CONVERTING THEM TO HEAT, THE IMPROVEMENT WHICH COMPRISES USING AS THE HECTOGRAPH TRANSFER SHEET ONE WHICH DOES NOT ABSORB INFRARED RADIATION TO ANY SUBSTANTIAL DEGREE AND WHICH CARRIES A PRESSURE-SENSITIVE TRANSFER LAYER WHICH IS BASED UPON A CELLULOSIC FILM-FORMING BINDER MATERIAL CONTAINING A NON-VOLATILE COMPONENT WHICH IS NON-MISCIBLE WITH SAID BINDER MATERIAL AND WHICH IS SELECTED FROM THE GROUP CONSISTING OF OLEAGINOUS AND PASTY COMPOSITIONS, AND A QUANTITY OF SPIRIT-SOLUBLE IMAGING MATERIAL, AND THE TRANSFER LAYER SOFTENSD BUT IS NONFLUID AT TEMPERATURES BETWEEN ABOUT 150*F. AND 450*F., THE TEMPERATURE OF THE THERMOGRAPHIC PROCESS.

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