US2338091A - Screen stencil and method of making same - Google Patents

Description

f 1944- J. B. BRENNAN ET AL I 2,338,091

SCREEN STENCiL AND METHOD OF MAKING SAME Filed April 18, 1939 JOSEPH .a BEEN/VAN & LEONA' MAEsH P'atented Jan. 4, 1944 SCREEN s'rsncn. AND mz'rnon or MAKIN SAME Joseph B. Brennan and Leona Marsh, Euclid,

Ohio: said Marsh assignor to said Brennan Application Apru 1a, 1939. Serial No. 263,570 I 18 Claims. ('01. 101-1283) This invention relates to screen stencils and methods of making same and the present application is a continuation in part of our copending applications Serial No. 115,208 and No. 175,240

filed December 10, 1936, and November 18, 1937,

respectively.

As describedv in our copending applications aforesaid screen stencils having very important advantages over those heretofore'known can be produced by blocking the interstices of a screen such as a fine woven wire mesh with a metal chemically different from the material forming the screen. applying a resist to the plate so formed, for example by a photographic method, and then etching away the blocking metal in those portions of the plate which are not covered by the resist. The etching operation is carried, out preferably by a re-agent which will attack and dissolve the blocking metal but will not substantially attack the material of the screen. Screen stencils so producer. are accurate and durable and may be advantageously used for many purposes as, for example; for applying designs in enamel to metal or for applying designs to glass for various printing and dyeing operations as well as for signs and dials. v

' In our prior applications the preferred forms of screen. stencils comprised metallic screens filled with or attached to a metal chemically different from the material forming the screen.

" In screen stencils made according to this application we "preferably employ three different metals of different chemical characteristics ineluding a perforate member such as a woven wire screen'formed of one inorganic material such; as a metal, a metallic sheet of a different metal which is secured to theperforated member by a metallic bond formed of still another metal. By this combination of elements and, by the proper selection Of materials it is'poss'ible to provide screen stencils by which a design canbe reproj, 'duced with great accuracy and fidelity evendown if to very minute details. Further,.it is possible to provide screen stencils of varying thickness so that deposits of varying amounts of material can be'made in the subsequent screening operations.

By the methods described herein screen stencils made according to our invention can be effectively and economically produced.-

The essential characteristics the claims.

In the drawing Figure 1 is a plan view of a preferred form of screen stencil plate made according to our inventionand having a design etched are summarized in therein; Figure 2-is 'a sectional view of the plate indicated in Figure 1 taken along the line 22 of Figure 1 on a greatly enlarged scale; Figures 3,. 4, and 5 are diagrammatic illustrations showing steps of preferred methods of producing our 1 screen stencils.

As shown in Figures .1 and 2 a screen stencil made according to our invention preferably comprises a perforate member such as a Woven wire screen l0 having a thin metal plate It secured to one side thereof, the plate being bonded to the screen by another metal l2 which at least partially fills the interstices of the screen. The materials comprising the screen, the filling in metal l2 and the sheet II are preferably chosen so that they can be subjected to selective etching action whereby the material of the sheet ll may be etched away until the underlying material I2 is exposed and thereafter the bonding material 12 may be dissolved bya reagent which will attack neither the sheet I 1 nor the wires making up the screen l0. As an example of a procedure which we have found to be very satisfactory a stainless steel screen! of about 150 meshwoven of wires about 0.002 in diameter may be sandwiched between a piece of tinfoil I 2 of about 0.004" thickness and Further novel features and advantages of our invention will become apparentfromthe follow- 5 ing description of preferred forms therjof, referme being made to the accompanyin a piece of copperv foil ll' of about .002" thickness as indicated diagrammatically in Figure 3. The three pieces may then be pressed tightly between steel plates or rolls, one-or both of which-may be heated sufficiently to cause the tin to melt. If

desired, the tin can be pressed into the screen by a fluid under pressure, or by a resilient or yieldable material such as rubber, and thereafter subjected to heat. The result of this process'is that the interstices of the stainless steel screen are filled as shown in Fig. 2, with tin, which also functions to secure the copper foil to the stainless steel screen.

In utilizing such a plate in' the manufacture of a screen stencil a resist may be applied to the flat surface of the copper in a manner known to those killed in'the art for example by the usualphotographic methods. Then the plate may be etched by an etching solution or solutions which will attack the copper and tinwithout substantially affecting the stainless steel wires; A solution of ferric chloride in water is suitable.

By this method the possibility of side etching oil the copper toll is eliminated and thus fine details may be accurately preserved. The result or the etching is indicated diagrammatically in Figure 2, wherein it will be seen that the copper and the tin have been removed in region Ill, leaving only the stainless steel wires. The copper toll is etched with sharp edges as at It, thus accurately preserving the detail or the design. even though the tin may be subjected to some side etching as shown at I! in Figure 2.

It will be noted thatthe screen is preferably spaced slightly above the flat surface ofthe copper foil as' shown in the drawing. When such screen is used for example in applying an enamel design the flat surface I8 01' the copper sheet is placed in contact with the article to which the design is to be applied and powdered enamel or frit is rubbed through the screen onto the surface which is to receive the design through the apertures such as the opening it. The sharp,

clearly defined edges I 6 of the etched areas in-- sure the production of accurate designs with all details properly reproduced. Also by varying the thickness of the copper foil, the distance between the. screen and the flat surface ll can be varied which will result in a corresponding variation in the amount of material or pigment deposited on the surfaces beingdecorated during the screening operation; that is, if the distance between the surface ll! of the copper foil and the screen is increased, a greater thickness of enamel or frit can be deposited while, if the distance is reduced, a thinner layer will be deposited. In carrying out .enameling'operations we are able, by employing foils of sufficient thickness, to deposit enamel in such quantities that the design will appear definitely in relief after it has been fired, and yet by reason of the sharpness of the edges of the etched-away portions and the smoothness and flatness of the surface it, there is practically no loss of definition.

Various other methods of securing the screen to the plate may be employed. Foa example, as shown diagrammatically in Figure 4 a screen Ila this means the sprayed tin will cause the copper sheet to adhere to the screen. Ifdesired, the sprayed assembly may be subjected to heat or pressure or both to compact the spray deposited metal and to bond the three metals more firmly together.

' Various modifications and changes may be made in the methods and articles describedherein. For example, the screen'may be-partially or completely filled in by dipping the screen in mol- .ten tin and then removing the excess or by electro-plating the screen with'tin. Thereafter the coated screen maybe assembled with a sheet of copper and subjected toheat, and pressure if desired, to form a unitary assembly. In every case, suitable flux may be employed to cause the materials to adhere properly. Various other materials may be substituted for those described herein. Thus the copper sheet or foil may be replaced by an iron sheet or foil in which case the iron may be etched by a solution of copper sulfate and hydrochloric acid, and thereafter the tin may be removed ride. (FeClz).

Zinc foil or nickel foil may also be employed, with the selection of proper etchants. Other metals, such as low melting point alloys, may be substituted for the tin described herein. The screen may be made of various materials such as Monel metal or bronze. The screen may be composed of any suitable perforate material such as a thin perforated metallic sheet or, if desired, parallel closely spaced wires may be used in place of woven wires. Variations may also be made in the methods of bonding. These and other modifications of our invention will be readily understood by those skilled in the art. Therefore it is to be understood that our invention is not limited to the preferred forms thereof disclosed herein, or in any manner other than by the appended claims when given the range of equivalents to forming the screen and'having an imperforate may be employed in conjunction with a sheet of copper foil Ha tinned as indicated at lZa. The

screen is placed against the tinned surface of the copper foil and pressed into the tin preferably by a roll or plate heated to a suilicient temperahire to cause the tin to melt or to become plastic.

The amount of pressure required will, of course,

be increased if the degree of heating is reduced.

The tin may also be cold pressed in or'hammered in as by a drop hammer. By varying the thickness of the tinand by subjecting the screen cally in Figure 5. According to this method a stainless steel screen lflb may be superposed upon a copper plate I lb and then the assembly sprayed with finely divided molten particles of tin for example by a Schoop pistol indicated at l9. By

metallic sheet bonded to said screen by said fill ing-inmetal, and subjecting certain areas of the plate to the action of a reagent adapted to dis-. solve said metallic sheet and said filling-in metal without substantially attacking the material of the screen, thereby dissolving the metallic sheet and the fllling-in'metal without dissolving the screen in-such areas.

2. A method oi'making screen stencils which includes the steps of forming a screen stencil plate comprising a screen of corrosion-resisting material having the openings therethrough at least partially closed by a layer of tin adhering thereto, and having an imperforate copper sheet bonded to said screen by said tin, and subjecting certain areas of said plate to the action of a re-' agent adapted to dissolve said copper sheet and said tin without substantially attacking the screen, thereby dissolving the copper and the tin without dissolving the screen in such areas.

3. A method of making screen stencils which includes the steps of forming a screen stencil plate comprising a stainless steel screen having the openings therethrough closed by a layer of tin adhering thereto, and having an imperiorate iron sheet bonded to said screen by said tin, and subby a solution of iron chloa,sse,oe1

thereto, and thereafter.,,etching,away the metal.

Iecting certain., .areas ofvsaid plate-to theaction l of a reagent adapted to dissolve said iron sheet and said tin without substantially attacking the stainless steel screen, thereby dissolving the copper and the tin without dissolving the screen in such areas. Y

4. A method of making screen stencils which includes. the steps of forming a screen stencil plate comprising a screen having the openings therethrough closed by a filling-in metal chemically different from the material forming the screen and having an imperforate metallic sheet bonded to said screen by said filling-in metal, applying a resist to a portion of the area of said plate, subjecting the, plate to the action of a reagent adapted to dissolve said metallic sheet until said metallic sheet is dissolved away in the areas of said plate which are not protected by said resist, and thereafter subjecting the plate to the action of a reagent adapted to dissolve said filling-in metal without substantially attacking said metallic sheet, the material of the screen, or the resist.

5. The method according to claim 4, wherein the screen is composed of stainless steel, the filling-in metal consists of tin. and the metallic sheet consists of copper.

6. A method of making screen stencils which includes the steps of forming a screen stencil plate comprising a stainless steel screen having the openings therethrough closed by a layer of tin and having an imperforate copper sheet bonded to said screen by said tin, applying a resist to a portion of the area of said plate; subjecting the plate to the action of a solution of ferric chloride until said copper sheet is dissolved away in the areas of said plate which are not protected by said resist, and thereafter subjecting the plate to the action of a solution of cupric chloride to dissolve said tin without substantially attacking said copper sheet, the screen or the resist.

7. The method of making screen stencils which includes the steps of bonding a metallic sheet to a metallic screen composed of a metal diflerent trom the metal of the sheet by means of a. bonding metal different from both the metal of the sheet and the metal of the screen, applying a resist to a portion cit the exposed surface of the sheet, and etching away the sheet and the bonding metal in the areas not protected by the resist without substantially etching the screen.

8. The method according to claim 7 wherein a copper sheet is bonded to a stainless steel screen by tin.

9. The method of making a screen stencil which includes the steps of placing a sheet of metal having a relatively high meltins p int in contact with one side of a metallic screen composed of a different metal, placing a sheet of metal having a relatively low melting point adjacent theother side of said screen, fusing the low melting point metal without fusing the metal of the screen or the'high melting point metal, to thereby fill the interstices of the screen and to bond the relatively high melting .point metal of the sheet and the bonding metal in certain areas without substantially etching the screen in such areas. a

10. The method of'making a screen stencil which includes the steps of assembling a sheet of metal having a relatively high melting point with a metallic screen composed of a different metal and a sheet of a metal having a relatively low melting point, and fusing the low melting point metal without fusing the metal of the screen orthe high melting point metal to thereby 1111 the interstices of the screen and bond the relatively high melting point metal thereto.

11. The method according to claim 10 wherein the high melting point metal consists of copper and the low melting point metal consists of tin.

12. The method of making screen stencils which includes the steps of disposing a metallic screen upon a sheet of another metal, spraying finely divided molten metal thereon to bond the screen and sheet together, and thereafter etching away the metal of the sheet and the bonding nietal in certain areas without substantially etching the screen in such areas.

13. The method of making screen stencils which includes the steps of disposing a stainless steel screen upon a sheet of copper, spraying finely divided tin thereon to bond the screen and sheet together, and thereafter etching away the tin and the copper in certain areas without substantially etching the screen in such areas.

14. The method of making screen stencils which includes the steps of bonding a layer of metal to a sheet composed of a metal having a higher melting point than the metal of the layer, heating the layer to soften it and embedding a metallic screen therein, the metallic screen being composed of a metal different from the metal oi the layer and the metal of the sheet. and themafter etching. away the sheet and metallic layer in certain areas without substantially etching the screen in such areas. I

15. In themanufacture of screen stencils of the tin and embedding a stainless steel metallic 7 screen therein.

17. A screen stencil blank or plate adapted to have a design etched therein comprising a stainless steel screen bonded to a sheet of copper metal .by a bond composed of tin.

18. A screen stencil blank or plate adapted to have a design etche'd therein comprising a layer of tinembedded in a fine meshed metal gauze attached to a thin layer'of copper.

I JOSEPH B. BRENNAN.

LEONA MARSH.

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