US3283704A

US3283704A - Electrosensitive facsimile stencilforming blanks

Info

Publication number: US3283704A
Application number: US345762A
Authority: US
Inventors: Harold R Dalton
Original assignee: Timefax Corp
Current assignee: Timefax Corp
Priority date: 1964-02-18
Filing date: 1964-02-18
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08
Also published as: FR1401568A; GB1071522A

Description

H. R. DALTON Nov. 8, 1966 ELECTROSENSITIVE FACSIMILE STENCIL-FORMING BLANKS Filed Feb. 18, 1964 2 Sheets-Sheet l M wmwuwmwfim u 1! m iurr @m a X usiwwwwnk 93 n {Ev Mo uuu m H. R. DALTON Nov. 8, 1966 ELECTROSENSITIVE FACSIMILE STENCIL-FORMING BLANKS r 1 N R WA o ND 5 AA. a 0 A e mm z fl 2 M K Filed Feb. 18, 1964 United States Patent 3,283,704 ELECTROSENSITIVE FACSIMILE STENCIL- FORMING BLANKS Harold R. Dalton, Jenkintown, Pa., assignor to Timefax Corporation, New York, N.Y., a corporation of New York Filed Feb. 18, 1964, Ser. No. 345,762 1 Claim. (c1. 101-128.2)

This invention is a continuation-in-part of US. application SN 658,074, filed May 9, 1957 (now abandoned) and relates to stencil-forming blanks, and more particularly it relates to blanks which are electrosensitive to applied electric signals to produce a perforated stencil record of such signals.

Another object is to provide an electrosensitive facsimile recording blank which consists of a normally non-conductive plastic film which has powdered carbon homogeneously distributed through the body of the plastic and which has also embedded in the plastic a sheet of foraminous material such as a finely woven fabric having retic-ulations or openings of uniform dimension, which openings are bridged by the said conductive plastic.

Another object is to provide an electr-osensitive stencilforming blank wherein the body of the blank is constituted of a conductive layer which is substantially free from fibrous stock such as Yoshino paper and the like.

Another object is to provide an improved electrosensitive film which can be perforated under control of applied electric voltages to produce a screen which is useful in any silk screen printing or duplicating process.

A feature of the invention relates to a novel electrosensitive stencil-forming blank which has strata of different electric conductivities, at least one of the strata having embedded or incorporated therein a foraminous sheet or film having perforations of uniform dimension so as to impart more precise perforation .of the blank in minute areas under control of stylus applied electric voltages.

A further feature relates to an electrosensitive stencilf-orming blank comprising a backing member to which is strippably attached with a low degree of adhesive affinity a film consisting of conductive plastic of graded or stepped conductivity considered through the thickness of the film, one portion of the plastic thickness having embedded or incorporated therein a foraminous sheet such as a fine mesh silk fabric or the like.

A further feature relates to an improved silk screen stencil.

A still further feature relates to the novel organization, arrangement and relative location and composition of parts which cooperate to provide an improved facsimile recording blank.

Other features and advantages will be apparent after a consideration of the following detailed descriptions with the attached drawing and the appended claim.

In the drawing:

FIG. 1 is a top plan view in magnified form of a section of a blank according to the invention;

FIG. 1a is a highly magnified sectional view of FIG. 1, taken along the line 1a1a;

FIG. 2 is a schematic diagram of an organization of apparatus for making the blank of FIG. 1;

FIGS. 3, 4, and 6 are magnified sectional views taken, respectively, along the lines 3-3, 44, 5-5, -6-6, of FIG. 2;

FIG. 7 is a composite sectional view of a blank and method of perforation according to the invention;

FIGS. 8 and 9 are magnified cross-sectional views of modifications of the blank according to the invention;

FIG. 10 is a schematic diagram of, another organization of apparatus for making the preferred form of the blank;

FIGS. 11-15 are cross-sectional views taken along the respectively identified cross-section lines of FIG. 10;

FIG. 16 is a magnified cross-sectional view of the preferred form of the blank;

FIG. 17 is a magnified cross-sectional view of a modification of FIG. 16;

FIG. 18 is a magnified cross-sectional view of a further modification of FIG. 16.

The present invention provides an electrosensitive signal recording blank such as is generally used in facsimile reproduction systems, and is in the nature of an improvement on the kind of blank disclosed in my prior Patent No. 2,664,043, although in certain of its aspects the invention is not limited to that general kind of blank. One form of the blank according to the invention is shown in highly magnified top plan view in FIG. 1, and in highly magnified sectional view in FIG. 1a and in FIG. 6.

The blank comprises a unitary composite sheet consisting of a specially prepared conductive plastic 10, such for example as any of the well known vinyl resins of which vinyl chloride-vinyl acetate copolyniers, vinyl chloride polymers, vinylidine chloride copolymers, styrene polymers, are typical. Integrally embedded in part of the blank thickness, preferably so as to be substantially entirely below the upper surface of the plastic film, is a sheet or film 11 of foraminous material. The material 11 is preferably of a woven, knitted, matted or netted fabric of silk, cotton, nylon, Dacron, rayon, or other natural or synthetic fibre. That is to say, the fabric should have mesh openings which are of substantially uniform size and distribution and extend substantially uniformly transverse to the surface of the fabric. Since the size of the mesh openings to a certain degree controls the fineness and uniformity of electrical perforation of the blank, as will be described hereinbelow, preferably, although not necessarily, the mesh should be equivalent to a woven fabric having for example to 400 threads per inch, the threads being approximately one to several thousandths inch in diameter.

In one form shown in FIGS. 1 and 6, the plastic may be formed in two succesive passes to form two

strata

10a, 10b, with the stratum 10a by itself being of much lower electric resistance than the stratum 10b by itself. Of course when the plastic film 10 as a whole is made by the two-pass process, the two

strata

10a and 1% are compatibly bonded to form, in effect, a unitary film having the desired combined electric. conductivity through the film thickness. Thus, by way of example, the stratum 10a may have a dry thickness of approximately 0.0002 inch to 0.0008 inch, with a surface electric resistance in the film of approximately 500 to 2000 ohms as measured between contacting surface electrodes, as described in my prior Patent 2,664,043. The stratum 101) may, for example, have a dry thickness of approximately 0.0005 inch to 0.005 inch. The combined thickness of the stratum 10a and stratum 1012 with the foraminous sheet 11 embedded therein, need not exceed 0.006 inch and the combined surface resistance of the two strata when measured by two electrodes spaced apart one centimeter, as described in Patent 2,664,043, may be between 500 and 1,000,000 ohms. The foraminous sheet or film 11 may be embedded or incorporated in the stratum 10b of lower conductivity. However, under certain circumstances the forarninous sheet or film may be embedded or incorporated in the stratum 10a of higher conductivity, as shown in the magnified cross-sectional view of FIG. 8, or it may be incorporated in an additional stratum as shown in FIG. 16.

One of the advantages of a blank according to the invention, over the prior blank as shown in my prior Patent 2,664,043, is that by reason of the iow stretch and ing as compared with paper stock blanks.

are applied to the stylus 15.

high tensile strength of the foraminous sheet 11 which forms an integral embedded part of the blank, the blank as a whole is free from undesirable stretching or dimensional distortion during handling or stripping. In such a facsimile blank which does not contain the embedded foraminous or woven fabric, since the plastic blank requires the presence of softening agents during its manufacture, the plastic possesses a considerable degree of stretchability somewhat similar to rubber film. Such stretchability .is undesirable in certain fields of utility. Furthermore, by incorporating the uniformly foraminous woven fabric 11 in the conductive plastic, the blank is substantially free from non-uniform stretching and is less likely to be destroyed by accidental ripping, tearing, or the like. This is particularly true when the blank is attached in a strippable manner to a backing sheet from which it is to be stripped after the electrical perforation of the plastic blank has been effected.

Another advantage over the prior electrosensitive blanks of the kind which rely on a paper or fibrous stock, such as Yoshino paper, is the ability to control the per unit area conductivity with more uniform precision. F urthermore, the plastic is essentially non-absorbent to moisture as compared with paper stock. Also it has a higher order of anti-creasing since the incorporation of the plastic, which is essentially an elastomer, enables the blank to be handled and stored without too much danger of creas- Furthermore since the blank is in effect a continuum of plastic in a foraminous non-fibrous base, its mechanical resistance to wear, tear and the like is substantially increased.

Since the over-all thickness of the blank is relatively small, for example of the order of approximately 0.006

inch, the likelihood of ripping or dimensional distortion is greatly reduced by the inclusion of the foraminous fabric 11, and the blank remains in a perfectly flat shape and free from the tendency to curl, buckle, or assume other non-fiat shape. Since the blank is designed especially to be perforatably responsive to applied point-like electric discharges, its electrical conductivity is of great important as compared with the conventional silk screen stencil designed to be perforated by mechanical or chemical means. Accordingly the blank is especially designed for use in any conventional electric facsimile recording machine employing a needle or similar pointed stylus electrode. Thus, as shown in FIG. 7, the blank of FIGS. 1, 6, 8 and 9 can be supported on a suitable conductive mem=ber 12 which may take the form of the grounded metal platen or metal drum of any well known facsimile recording machine 13.

The drum 12 may, by any conventional means, he rotated around its axis at a predetermined scanning rate so as to be synchronized with a similar scanning drum at any conventional facsimile transmitter, which transmitter constitutes the source 14 of the facsimile electric signals. These signals are received and amplified and applied to a needle electrode or stylus 15 which is arranged to be moved along the length of drum 12. In other words,

the lights and shades of the successive elemental areas of the subject matter at the transmitter are converted by well known facsimile methods into electric signals which As a result of the electric conductivity characteristics of the blank 10', it becomes perforated through its thickness, as indicated by the nu- -meral 16. These perforations are of minute cross-section and may be as small as 0.0005 inch in diameter.

One of the problems encountered in making conductive plastic blanks is to insure that the blank has, for

an applied electric signal voltage of a given amplitude, .uniform perforatability over its entire recording surface.

I have found that by incorporating the uniform foraminous sheet or film 11 in the body of the conductive plastic act to prevent undesirable mushrooming of the discharge away from the very minute area beneath the point of the electrode 15. Therefore, by making the openings 17 of extremely minute size it is possible to perforate the blank in more sharply confined regions beneath the stylus. Furthermore, with such a blank the danger of the blank being cut out along a continuous line as a result of a continuous discharge moving along the surface of the blank is avoided, since only the plastic portion of the blank is perforated by the signals. The unrecorded reminder of the blank remains intact, thus preventing a completely continuous slit being formed.

It will be understood, of course, that in the -art of facsimile transmission and reproduction, the signal voltages used for recording are of a relatively low value, for example of the order of 200 to 500 volts. For that reason there is a practical limit to the over-all thickness of the blank for satisfactory recordings, which thickness need not be substantially greater than 0.006 inch. Furthermore, because of such thickness limitations, the highly conductive stratum 10a is usually of extreme thinness, for example between 0.0002 inch and 0.0008 inch. In that case it is not feasible to embed the foraminous material or film 11 completely in the highly conductive stratum 10a. Preferably, therefore, the lower conductivity stratum 10b can be made slightly thicker than the stratum 10a so as to facilitate the embedding of the foraminous fabric 11 therein and so as not to cause any substantial part of the fabric to project above the upper surface of the stratum 1%. If desired, instead of using paper or other similar insulating material for the backing 20, that backing may be of conductive material to which the blank is strippably attached. For example as shown in cross-section in FIG. 9 the blank can be strippably attached to a metal foil backing 32. This enables the backed blank to be packed or stored more conveniently, and after the composite plastic-foraminous screen blank proper has been perforated by the facsimile signals, it can be readily manually stripped from its backing for use in any well known silk screen or other multireproducing system. When the recording takes place with either the paper backed blank or the metal foil backed blank, only the blank proper is perforated, the backing remaining unperforated. But when the blank is stripped from its backing the latter carries a duplicate carbon record of the signals. However, the blank can be recorded on without the backing sheet.

Referring to FIG. 2 there is shown in schematic form one method of manufacturing the backed blank. The backing material 20 in the form of a smooth-surfaced paper or metal foil, cardboard, or plastic web, is drawn off a supply reel 21 and is supported on an endless belt or conveyor 22 which is driven in the direction of the arrow, thus carrying the backing web 20 towards the receiving reel 23 which may be driven at the same rate of speed as the conveyor 22. If the web 20 has its smooth dense surface on one side only, the web is unreeled from the reel 21 with that smooth surface uppermost.

The web 20 passes the discharge opening of any well known applicator device 25 which contains the plastic 10a in liquid form so as to apply to the smooth surface of web 20 a film of that plastic which when dry will have the required thickness, for example of 0.0002 to 0.0008 inch. It will be understood, of course, that the device 25 is merely schematically representative of any well known coating mechanism, whether of the roll, brush, spray or knife coating kind, for applying the requisite metered film of conductive plastic 10a to the backing web 20. The web 20 carrying the coating 10a is then subjected to any heating or drying operation represented schematically by the dryer 26, so as to leave a dry coating 10a on the backing. The coated backing is then carried past another coating device 27 which may be similar to the device 25, for applying the conductive plastic film 10b over the dry film 10a. Immediately after being coated with the film b, and while the latter is still in a liquid or semi-liquid condition, a web of the foraminous film or fabric 11 from a suitable supply roll 28 is laid on the coating 10b and, if necessary, it may be subjected to a light rolling pressure by suitable pressure rolls 29, 30 so as to embed the fabric 11 into the body of the viscous plastic film 10b.

The composite backing with the two plastic coatings is then subjected to another heating or drying operation represented schematically by the dryer 31. The dried composite material comprising the backing 20 and the two hardened conductive plastic and

fabric coats

10a, 10b (and 11) are then reeled on the receiving reel 23. The reel 23 can be stored and the composite backed plastic blank can be cut into suitable lengths or sizes by any well known cutting device (not shown).

If desired, prior to reeling the composite blank on the reel 23, the exposed upper face of coating 10!) may be provided with a masking coating of contrasting shade with respect to the coating 10b. This masking coating may be of the kind disclosed in US. Patent 2,664,043 and is merely of sufiicient thinness to provide a lightcolored appearance to the upper surface of the blank. By upper surface is, of course, meant that surface of the blank which is adjacent the recording stylus (FIG. 7). Thus the recording can be visually observed during the recording operation.

While the blank can be manufactured with a backing strippably attached thereto, it will be understood that the invention is not necessarily limited thereto. For example the blank consisting of the

strata

10a, 10b, with the embedded foraminous fabric 11, may be cast or coated directly onto the surface of the conveyor belt 22, that is, without the paper backing 20. The belt 22, of course, will be of a suitable material such as stainless steel or other hard smooth surface material from which the dried composite plastic-foraminous fabric blank can be stripped.

While in the foregoing embodiments, the foraminous fabric is incorporated or embedded in either the low conductivity stratum 10b (FIGS. 1:: and 6), or in the high conductivity stratum 10a (FIG. 8), I have found that, if desired, the foraminous material can be incorporated in a third conductive plastic stratum. In any case, the particular stratum of plastic into which the foraminous material is incorporated, as shown in FIGS. 1a, 6 and 8, is, preferably, approximately equal to the thickness of that stratum. Thus as shown in FIGS. 1a and 6, the foraminous material 11 has a thickness which is approximately the same as the thickness of the stratum 10b, whereas in FIG. 8 the foraminous material 11 has a thickness which is approximately the same as the thickness of the stratum 10a.

I have found that for certain applications when the foraminous material or fabric is completely embedded in or otherwise bonded to that stratum while the latter is viscous, it is not always possible to control precisely and maintain the desired uniform con-ductivity of that stratum. I have also found that improved characteristics are obtained in the finished blank if, instead of embedding or incorporating the foraminous fabric or material directly in the low conductivity stratum 1%, it is incorporated or embedded partially or wholly in a third stratum which is applied separately to the stratum 10b. The conduc- .it does not disturb or change the predesigned uniform conductivity or resistance of the stratum 1012. Such a .typical blank is shown in magnified cross-sectional view ,in FIG. 16.

It may consist of the paper or cardboard 6 backing 20 with the high conductivity stratum 10a, the low conductivity stratum 10b and with a third stratum 10c11.

Referring to FIG. 10 there is shown in schematic form a preferred method of manufacturing the preferred blank shown in FIG. 16. The parts illustrated in FIG. l10 which are similar to corresponding parts of FIG. 2, carry the same designation numerals. In the arrangernent of FIG. 10 there is an additional applicator device 33 which contains the conductive plastic in liquid form. The material 10c is applied on the stratum 10b after this latter stratum has been dried by passage through the dryer 26a thus forming a third conductive stratum 10c. Immediately after application of the stratum 10c and while the latter is still in a liquid or semi-liquid condi tion, a web of the foraminous fabric or film 11 is fed from a supply roll 28 and applied to the viscous stratum 10c. The foraminous material 11 may be lightly laid or lightly pressed into the viscous stratum 10c by a light pressure guide roll 29. The composite assembly is then dried in a suitable dryer 31 to permanently bond the foraminous material 11 to the assembly. This assembly 35 is preferably left on the backing 20 until after the blank has been recorded. However, if desired instead of using a paper backing 20 for the blank, the conveyor belt 22 may be of a dense smooth surface material such as stainless steel or the like. In that case, the paper backing 20 and its supply reel 21 can be omitted. Thus the stratum 10a can be applied directly on to the surface of the conveyor 22. After this composite assembly passes the dryer 31, it can be stripped from the conveyor 22 by any well known stripping device, schematically represented by the numeral 36.

Preferably the thickness of the composite stratum (10c, 11) is such that it does not materially increase the thickness of that composite stratum beyond the thickness of the'foraminous fabric or film 11 itself. This condition is illustrated in the cross-sectional view of FIG. 16 wherein the openings in the material 11 are shown as filled with the conductive plastic 100. It is not necessary that these openings in the material 11 be completely filled to the surface of the fabric as long as the conductive plastic 10c bridges the walls of the respective openings in the foraminous material. This relation is shown in the highly magnified cross-sectional view of FIG. 17 wherein the foraminous fabric or fihn 11 has its openings 37 bridged by the conductive plastic 10c, but the thickness of this plastic in each opening is somewhat less than the thickness of the foraminous materal 11.

Merely by way of example, the stratum 10a may have a dried thickness of 0.0002 inch to 0.0008 inch and it may have a surface resistance of from 500 ohms to 2,000 ohms. The stratum 10b may, for example, have a dried thickness of approximately 0.0005 inch to 0.005 inch and may have a surface resistance of from 500 ohms to 1,- 000,000 ohms. Likewise, the composite stratum (10c, 11) may have a thickness of approximately 0.0001 inch to 0.003 inch. Or stated in terms of the foraminous fabric or material itself, the composite stratum (10c, 11) may have a thickness equal to the thickness of the material 11 or slightly more than the thickness of the material 11 and it may have a surface resistance of from 500 ohms to 10 megohms.

The finished composite blank assembly, a portion of which is shown in magnified cross-sectional view in FIGS. 15 and 16, therefore consists of the backing 20 to which is adherent in a readily strippable manner, the composite assembly or web 35 comprised of the highly conductive base stratum 10a, the lower conductive stratum 10b, and the composite stratum (10c, 11). This assembly 35, as hereinabove described, forms a unitary web or film, for example, of 0.008 inch total thickness which can be readily stripped from the backing 20. Prior to stripping from the backing 20, the blank can be recorded upon in transversely to the surface of the fabric.

7 the manner described above in connection with FIG. 7 as a result of which the blank assembly 35 is perforated by the recording signals and thus forms a duplicating stencil which can be stripped from the backing 2.0.

The invention is not limited to any particular kind of resin that may be used for the

coating batches

10a, 10b, 100. These batches may be any of the vinyl resins of which vinyl chloride-vinyl acetate copolymers, vinyl chloride polymers, vinyl vinylidine chloride copolymers, styrene polymers, etc. are typical. The material 11 is preferably of a woven, knitted, matted or netted fabric of silk, cotton, nylon, Dacron, rayon, or other natural or synthetic threads and preferably formed from monofilament threads. The fabric should have mesh openings which preferably are of substantially uniform size and distribution and extend substantially, uniformly, Since the size of the mesh openings in material 11 may, to a certain degree, control the fineness and uniformity of electrical perforation of the blank, preferably, although not necessarily, the mesh should be equivalent to a woven fabric having, for example, 100 to 400 mono-filament threads per inch, the threads being approximately one to several thousandths inch in diameter. In any event, the fineness 'of the mesh should be correlated with the fineness of the perforation recordings to be effected in the blank. For

example, the mesh may be correlated with the size and spacings of the recorded perforations so that when copies are made from the stencil they approximate the quality of the usual rotogravure half-tone reproduction. It should also be understood that the invention is not limited to 'the material 11 being a woven fabric.

It may be in the form of any well known uniformly perforated film having the desired tensile strength equivalent to that of a woven fabric as distinguished from paper materials such as Yoshino paper and the like.

One of the advantages of the blanks hereinabove described is that by reason of the low stretch and high tensile strength of the material 11 which forms an integral part of the finished blank, the blank as a whole is free from undesirable stretch or dimensional distortion during handling or stripping. It also has important advantages over the prior blanks using a paper base such as Yoshino paper. Since the overall thickness of the conductive film portion of the blank is relatively small, for example, in the order of 0.006 inch, the likelihood of ripping or dimensional distortion is greatly reduced and the blank remains in perfectly flat shape and free from a tendency to curl, buckle, or assume other non-fiat shape. Since the blanks are designed especially to be perforatably responsive to applied point-like electric discharges, their electrical conductivity is of the essence as compared with the conventional silk screen stencil which is designed to be perforated by mechanical or chemical means. The blanks according to the invention are especially designed for use in any conventional electric facsimile recording 11 of extremely minute size, it is possible to perforate the blank in more sharply defined elemental regions beneath the recording stylus. Furthermore, the danger of the blank being slit along a continuous line as a result of a continuous discharge moving along the surface of the blank is avoided since only the conductive plastic portion of the blank enclosed within the foraminous openings of material 11 therein are perforated by the signals. The remainder of the blank between the recorded perforations remains intact, thus preventing a completely continuous slit being formed.

It will be understood, of course, that in the art of facsimile transmission and reproduction the signal voltages used for recording are of a relatively low value, for example, to the order of 200 to 1,000 volts. For that reason there is a practical limit to the overall thickness of the conductive portion or assembly 35 of the 'blank for satisfactory recordings and this thickness need not be substantially greater than 0.006 inch. After the blank has been recorded upon by being perforated it can be used in any well known silk screen or other multi-reproducing system, such for example as illustrated in US.

Patent No. 3,081,698.

As hereinabove pointed out, the strippa-ble backing for the blank instead of being of paper or cardboard 20 may be of metal foil 32, as illustrated in FIG. 9. While FIG. 9 shows the foraminous material 11 incorporated in the stratum 10b, the blank of FIG. 9 may be modified as illustrated in FIG. 18, so that the metal foil backing 32 acts as a high conductivity stratum to which is applied the low conductivity stratum 10b and then there is applied to the stratum 1011 a composite stratum (10c, 11).

While in the foregoing it has been mentioned that the foraminous material or fabric 11 has been applied directly to the viscous material 10c, if desired, the foraminous fabric or material 11 may be prepared in any well known manner so that the filaments thereof are pre-coated with any suitable conductive material such as the same material for the batch 10c but without substantially filling the pores of the fabric. In other words, even though the fabric 11 is thus pre-treated, when it is applied or lightly laid on the viscous stratum material 10c, the fabric must have sufficient porosity to enable the solvents of the stratum to 'be removed in the dryer 31 by passage through the pores of the pre-treated fabric.

Inasmuch as the various form of blanks hereinabove described contain powdered carbon as the conductive ingredient, the upper surface of each blank will therefore have a blackish appearance. If desired, this blackis-h surface may be coated with a thin masking coating of a suitable whitish masking material containing a whitish pigment such as zinc oxide, zinc sulfide in a suitable binder, or any other well known masking coating such as described, for example, in my prior Patents 2,554,017 and 2,664,063. Merely for simplicity, this masking coating is indicated 'by the numeral 38.

While in the foregoing reference has been made to the foraminous film 11 as being of silk or other natural or synthetic fabric which is formed of insulating strands, for certain applications the film 11 may be formed of metal mesh of the desired fineness and porosity above noted. It may also be a metal foil which has been perforated by any well known process to provide a multiplicity of uniformly distributed perforations. These perforations should have the fineness and spacing equivalent to the mesh hereinabove referred -to.

While the expression silk screen has been used here-. in, it will be understood that it is used in the generic sense employed in the silk screen printing art, to include a screen constituted either of silk or other openwork mesh fabric, which may be formed of non-conductive strands or of conductive strands such as fine mesh metal cloth.

While various values, materials and proportion of parts have been mentioned herein, it will be understood that they are given merely for explanatory purposes and not by way of limitation on the claim attached hereto.

What is claimed is:

An electrosensitive blank for producing a record of electric voltages applied thereto, comprising a sheet of a continuous, self-sustaining, non-conductive, organic plastic, said sheet having a continuous plastic finish on its opposite surfaces, a non-conductive, foraminous member of 100 to 400 mesh incorporated in said sheet, said foraminous member having openings of uniform dimension, said sheet having powdered conductive particles 9 distributed throughout the body thereof to render the blank as a whole responsive to said voltages to make a permanent perforated record thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,194,899 8/1916 Strippel 101-1282 X 1,606,217 11/1926 Gestetner 101-128.2

Brush 117--128 Koreska et a1. 101426 X Nichols 101-128.2 Meigs 101-426 X Dalton 101--426 X DAVID KLEIN, Primary Examiner.

WILLIAM PENN, Examiner.