US 2351696 A
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Patented June 20, 1944 STENCIL AND STENCIL BACKING Wallace Hunter Nichols, Port Washington, N. Y., 7
assignor to Rodic Rubber Corporation, Garwood, N. J., a corporation of Delaware No Drawing. Application March 5, 1940, Serial No. 322,347
My invention in general, relates to improvements in stencil sheet and method of producing the same, of the kind of stencil commonly used for the reproduction of typewritten, manuscript or printed matter; drawings, photographs or the like, comprising a sheet or member of impressible fibrous material containing thereon or/and therein a non-cellulosic attached film or solution from which the evaporable portion has been removed, and the use of said stencil sheet in preparing a stencil therefrom.
Heretofore in the typeand stylus-impressible art, it has been customary to employ for a background upon which to spread the type-impressible substance, a sheet of fibrous matter, usually'a paper variously called Yoshino, Japanese or cobweb paper, and to place thereon on a single or multiplicity oi coatings, a cellulose derivative as nitrocellulose, containing in addition, various fatty, oily, waxy liquids and solids to impart softness, flexibility and water resistance to the composition. The bodies most often used for this purpose are castor and analogous oils, paraffin oil and solid paraffin hydrocarbons, beeswax, carnauba wax, Montan wax and the like, and high boiling aliphatic esters of monocarboxylic high molecular fatty acids.
In complicated mixtures of organic bodies such as the above, decomposition is prone to set in, the castor and other oils rancidiiy, the oils spew or come to the surface of the stencil sheet upon standing, 'stearic acid and waxy bodies bloom or form a white "efflorescence on the surface of the stencil sheet, and other disadvantages are apparent. The oils, fats and waxes used are supposed to exert a softening eilect upon the cellulose derivative employed, but the free acids generated upon standing have a deteriorating eiiect upon the cellulose ester, especially where nitrocellulose is used, the oils decompose, the waxes oxidize and harden, and other changes take place in a stencil sheet of this nature whereby its value for the purpose intended materially diminishes on keeping.
Furthermore, having once used such a stencil sheet of the present art, and having saturated the cellulose fibrous backing with the usual form of sticky, water-absorbing, water-soluble or oily stencil ink, it is difficult, if not well nigh impossible to re-use the same after standing a few days, primarily on account of impregnation of stencil coating by the softening, disintegrating, viscous stencil ink base, which, whether of aqueous or oily composition, is antagonistic to the cellulose derivative used as the basis of the stencil coating.
The above and other inherent disadvantages of the present used type of stencil sheet, depending"v upon liquid oily material to keep the cellulose derivative tractable, and which materially limits its application and diminishes its efliciency, is obviated in the present application, in that no nitrocellulose, cellulose acetate or other cellulose derivative, no castor or other oil, no tats or waxes are used, and there is no necessity for the employment of any added softening, extensifying, tempering, setting or similar agent.
My new and improved stencil comprises two dissimilar members, being a foundation sheet of fibrous cellulose in contact with a structureless, neutral, highly stable, elastic member, not adversely affected by extremes of normal atmospheric temperatures, and which retains its desirable characteristics for an almost unlimited period of time. My stencil sheet is highly moisture-proof, vapor-proof, relatively non-porous, non-yellowing, humidity-resisting, nearly transparent, may be colored by incorporation therein of dye, lake or pigment, stable to ultra-violet or sun light, and which repels moisture, withstands abrasion, is mildew-proof, not aflected by bacterial or fungicidal action, and possesses a high plasticity and extreme pliability coupled with unusual surface resistivity and relatively high dielectric strength.
As compared with the stencil sheet of the present and past art, stencil sheets mad according to my invention do not harden, oxidize, break down with age, evolve deleterious substances on standing, are long wearing, e sily cleaned for reuse, and substantially indestructible when used in an approved manner for the purposes intended.
It is practically impossible with a stencil sheet of the present art after having punctured the same with a multiplicity of characters, to re-use the same after having been softened by the saturation of oily ink and the stencil allowed to stand for several days. Attempts to wipe or brush oh the ink with which the backing is saturated,
especially when the ink contains hygroscopic substances like glycerin, which often is the case.
One of the main objects of my invention is to increase the wearability,. stability and permanency of a commercial stencil of the type-impressible class and having an easily deformable structure, and a surface of character suitable for obtaining a multiple of copies or impressions therefrom of typed, written or drawn characters, by means of the utilization of a novel and valuable form of material in conjunction with the Yoshino or similar paper of the present art to form the stencilizable portion of the stencil sheet, and to obtain a stencil therefrom by impact against the platen of a typewriter in the usual manner, or by interposing between typewriter and stencil sheet a woven material harder than is the stencil sheet substance, and of sufficient hardness so that impact of type or stylus thereon will produce a multiplicity of separate holes or apertures, through which ink may flow in obtaining impressions from said stencil.
In one preferred embodiment of my invention for producing an improved stencil backing, and an improved stencil therefrom suitable for stencilizing, I take a sheet of Yoshino paper and contact the same with a rubber halide or rubber hydrohalide (except the fluoride), either 'in solution, or after the solution has been cast into film form, and utilizing the latter.
Of the rubber halides or hydrohalides, I prefer to use the chloride or hydrochloride as it gives satisfactory results and at the present time is the least expensive of this group of compounds. I prepare a solution of the rubber compound in a suitable solvent or solvent combination, of the viscosity, total solids in solution, evaporative solvent speed and other characteristics desired, and immerse, flow on, spray on, or otherwise bring said solution in contact with said fibrous element in any approved manner. in a single or plurality of coatings, than allowing the solvent portion to disseminate by evaporation at normal or elevated temperature.
The solution permeates the fibrous cellulosic portion, filling the interstices and anchoring therein. One or both sides of the cellulose may be coated as desired, but I have obtained satisfactory results by coating one side only. No vegetable, animal or mineral fats, oils or waxes are used, and no softening, setting, or tempering agents added.
Where the rubber compound and cellulose are brought together, the coating increases the thickness of the cellulose layer from one to five times or more, depending upon the polymer degree of the rubber halide and the presence or absence therein of thermoplasticizing or similar agents. Depending upon the method of production, there is considerable variation in tenacity, viscosity and other characteristics of the rubber compound, and the amount of the same deposited upon or in or both, of the cellulose will depend in a measure upon these characteristics.
The cellulosic portion may be colored, or the impregnating solution may be colored in order to obtain a contrast color whereby the cut-out portions are more readily discernible in the finished stencil sheet. The addition of a relatively small amount of mineral filler, as pigment or tale in an impalpable condition imparts an opacity to the stencil sheet which diminishes its porosity, which under certain conditions is advantageous. Upon dissipation of solvent from the impregnated sheet, it is then in condition for stencilization, or the coated side may be smoothed and polished by running said sheet through rollers, or by applying pressure or pressure and heat thereto in other manner.
In an alternative manner of contacting cellulose material and rubber substance, I may first form a film of rubber halide or rubber hydrohalide, either of smoothed or roughened surface on one or both sides thereof, said film being but a few ten-thousandths of an inch in thickness, and the cellulose sheet and film then subjected to pressure or combined heat and pressure to produce a unitary member. Said member may be constituted of a single sheet of cellulose with either a film of rubber compound on both or one side thereof, or a single film of rubber compound with sheet of cellulose each side thereof.
The preferred thickness of rubber film or rub ber composition to be used in conjunction with the cellulosic member will depend in a large measure upon its relative plasticity and impressibility, and this in turn is governed by the physical characteristics of the rubber halide or rubber hydrohalide, or rubber hydrochloride used, and the thickness of the same in the attached condition relative to the cellulose matrix. Also as to whether the stencil cutting is to be made in the usual manner with a hard rubber platen as the backing, or whether the type impinges on a woven material interposed between platen and stencil during the stencilization operation. This is readily determined by the degree of type impressibility under the conditions existing.
With a relatively thin impregnation of cellulosic material with rubber hydrochloride in the dissolved condition, and removal of solvent therefrom a rubber platen may be used. 0n the other hand, where a thicker film has been attached to the cellulose on one side, or a thinner rubber hydrochloride film attached to the cellulosic member on both sides, better results may be obtainable by the interposition of a relatively hard woven material between sheet.
Where such woven material is employed, I have obtained excellent results by the use of a wire mesh cloth, such as a Monel, brass or bronze metal screen, of mesh, or preferably finer mesh. A 200 to 400 mesh screen gives excellent results in this connection.
By "rubber halide" or rubber hydrohalide, it is to be understood this expression includes rubber hydrocarbons and cyclocized rubber in the form of a halogen compound. These bodies combine extreme tenacity and stability, suppleness and impermeability, and admit of a clearly cut edge to the characters, an. important consideration when compared with the yielding fatty, waxy and oily composition of the present stencil sheet coating. This is especially evident in the cutting of small characters as degree or percentage or writings of chemical formulae (Car) or in the drawing of fine lines or shading in pictorial work.
Where relatively large numbers of mimeograph copies are desired, then it is advantageous to employ a Yoshino sheet with a larger amount of rubber compound impregnated in the interstices thereof, or a stencil sheet composed of a thicker film of rubber material attached to the Yoshino paper, or said paper sandwiched between two films of rubber hydrochloride, or said paper coated on both sides thereof by a single or plurality of rubber compounds in solution. In such instances it may be more advantageous to obtain platen and stencil the stencil by impingement of type against metal wire screen interposed between platen and stencil sheet, or the use of an abnormally hardened rubber composition platen.
Where a comparatively lesser number of stencil impressions is to be made, a single coated Yoshino sheet, Or a relatively thin rubber hydrochloride film attached to the Yoshino paper may be indicated for more satisfactory results, in which case the use of a woven hard surface between platen and stencil sheet may be dispensed with. For the ordinary class of work, a Yoshino paper having thereon or therein and thereon a rubber hydrochloride portion from one-half to ten thousandths of an inch in thickness, has been found to give a large number of copies of satisfactory appearance, and to be usable a number of separate times at varying intervals of time.
Where a woven material is inserted between typewriter platen and tencil sheet, upon contact of type bars with stencil sheet, the metal portion of the individual letters comes in contact,
or nearly so, with the ridges only of the woven material, and at those points of contact pierces the stencil substance with a series of points" or bars," apertures or cut-outs therein of nonuniformsize and shape, but at substantially equal distances, and corresponding to those points or places contact between type and portions of the weave where one filament or wire crosses another.
The result roughly is, that the stencil sheet contains a plurality 01' individual punctures which are separate one from the other, and the plurality of these individual holes represents the outline of the individual letter.
Through these minute orifices or punctures, representing an outline of the particular letter, ink exudes in reproducing copies made from the stencil sheet, to constitute the individual letter or character.
The number and/or size of these holes vary directly with the mesh or the indurated woven material with which the type comes in contact, being of a greater number and closer together,
conversion into a stencil as the mesh of the woven material increases per linear inch.
Due to the natural mobility and flowability o! be it aqueous or oil! in the usual stencil ink,
character, the ink upon penetrating into and through one of these tiny orifices, by virtue of the pressure behind the same, tends to ooze or spread out, so that the irregular pin points originally produced, tend to run together and coalesce on the paper, thereby forming what appears as a solid outline of the individual letter.
The portions or points between successive punctures in the backing sheet, consisting oi cellulosic fibers and rubber hydrohalide substance, form a skelet'onized framework, holding in position and without distortion the inner portion of such a letter as o. Heretofore in the stencil art, this inner portion was held together, if at all, only by means of the Yoshino interlaced fibers, and these fibers were prone to tear apart and distort by the normal pressure and friction incident to obtaining copies therefrom.
In the stencil sheet of this invention, we have the double strengthening of cellulose fibers and rubber hydrochloride substance.
The relative size of the punctures and distance between the same, may be regulated between comparatively wide limits by a selection of the fineness of mesh or the woven material and diameter and gauge of the individual wires if a wire mesh fabric be used, or the denier of the individual filaments, if a non-metallic woven material be employed.
When the requisite copies desired have been obtained from a stencil of the composition set forth in this invention, or its equivalent, the ink on the obverse side of the stencil sheet may be removed by brushing or wiping, and the stencil sheet stored for re-use at a future time, the stencil ink having no appreciable deteriorating action upon the stencil composition, due to the insolubility of the rubber hydrohalide in the ink components.
A stencil sheet consisting of a thin sheet of Yoshino paper impregnated with rubber hydrochloride to form a thin structureless composite non-plastic frangible and stencilizable film tor bampact of type thereough said composite WALLACE HUNTER H1013,
on forming perforations film.