US2355884A - Medium for use in making camera copy and method of preparing same - Google Patents

Description

Aug. 15, 1944. M. D. MCINTOSH MEDIUM FOR USE IN MAKING CAMERA COPIES AND METHOD OF PREPARING SAME Filed Aug. 15, 1942 INVENTOR. MAURICE D. MINTOSH 4% AT ToRNEYs Patented Au '-.j15,"1944 J UNITED mg MEDIUM FOR use in MAKING omens COPY AND METHOD SAME OF PREPARING Maurice D.- McIntosh, Cleveland Heights, Ohio,

asaignor to Louis S Sanders, Shaker Heights,

application august is, an, Serial No. assess '8 Claims.

This invention relates, as indicated, to a medium for use in making camera copy," method of preparing the same. In my ReissuePatent No. 20,503, I have deand to a scribed a drawing paper having a plurality of normally invisible patterns, one of the patterns being developable by a developer solution capable of developing said pattern only and both of the patterns being developable by a, developer solution capable of developing both of the patterns collectively. In the specific example described in said patent, one of the p'attems consists of a plurality of geometrically arranged dots located in equally-spaced diagonal rows in such a manner that the dots in one of the rows align with adjacent dots in the other rows to form diagonal rows extending transversely of the first-named rows. The other pattern consists 01 diagonal lines extending longitudinally of and in registry with the respective diagonal rows of dots.

While this method of forming the patterns is, in general, satisfactory, its value depends to a great extent on securing perfect registry or proper relative location between the dots and lines, a condition which is often exceedingly difficult to obtain by the ordinary method or forming the patterns, that is, printing the patterns I by means of plates.

I have discovered, however, that I can secure perfect registry or proper relativelocation between different patterns by the simple expedient of superimposing one pattern in the form of small dots, over another,in the form of larger dots, both patterns being formed in such a manner that registry between two diflerent printing plates, as described in my aforesaid reissue pateat, is not necessary. In the description which follows, the first or superimposed pattern will sometimes be referred to as the-flrst tone, and the other pattern, consisting of the small and large dots, will be referred to as the second tone.

The invention can probably best be understood by reference to the accompanying drawing, wherein,

Fig. 1 is a fragmentary perspective view, illus-.

trating the first stage in the manufacture of the medium of the present invention;

Fig. 2 is a fragmentary perspective view of a reverse dot printing plate which is used in making the medium;

' Fig. 3 is a view similar to Fig. 1, but showing the reverse dot printing plate of Fig. 2 in position to transfer the varnish thereon to the gelatin-coated surface or the sheet of Fig. 1;

Fig. 4 is a cross-sectional view of the assembled elements of Fig. 3; 4

Fig. 5 is a view similar printing plate removed;

Fig. 6 is a fragmentary plan view, on an enlarged scale, of the sheet shown in Fig.5;

Fig. 'l is aview similar to Fig. 6, but showing, in dotted lines, the extent of penetration of the lead acetate solution into the gelatin coating;

Fig. 8 is a view similar to Fig. '7, but showing, in dash-dot lines the extent of or area of the to Fig. 4, but with the mercurous nitrate dots;

, like.

Fig. 9 is a view similar to Fig. 8, but showing the appearance of the sheet after removal of the original varnish imprint and after development of the smaller dots, and

Fig. 10 is a view similar to the development of both dots.

Referring more particularly to the drawing, and especially to Fig. 1, I represents a base sheet, which may be of paper or a synthetic plastic film, such as cellulose acetate, ethyl cellulose, or the Baryta coated'paper, as used for thebase of photographic print paper is also suitable for this purpose.

To this base sheet is applied a thin coating 2 of plain gelatin of a thickness of from .001" to .002". This may be applied to the material by using an aqueous solution containing 10% by weight of plain gelatin, the solution being applied warm, using a whirl coating or roll coating machine, or any other means whereby a uniform gelatin coating of-the requisite thickness is obtained.

Instead of coating a base sheet with gelatin, a gelatin-coated sheet, available in the market. such for example, as imbibition paper furnished by Eastman Kodak Company, may be used.

A printing plate 3 is then prepared having a multiplicity of openings 4 therein, which are shown as circular, but which may be square or any other desired shape, these openings being spaced from each other in a manner similar to the spacing of dots in an ordinary Ben Day pattern. Such openings, in actual practice, are extremely small and spaced very closely together, but the size and spacing are greatly enlarged in the present drawing, for purposes of clarity. A film I of any water resistant printing varnish or ink is then applied to the plate 3 in such a manner that the varnish or ink covers the entire suri lace 4of the plate, with the exception of the open- The film 5 is then transferred directly to the Fig. 9, but showing gelatin film 2 of the sheet I, in the manner shown in Figs. 3 and 4, that is by ap lying the plate 3, varnished side down, to the film 2 oi the sheet. Instead of using a fiat printing plate, a cylin-v drical or rubber type of printing device having openings therein may be used to apply a film of varnish or ink to the film 2.

The plate 3 is then removed. leaving a, gelatincoated sheet, upon which is superimposed a varnish imprint, containing circular openings 2 forming a dot pattern, and through which the gelatin coating is exposed. v

The varnish print is then permitted to dry, whereby it becomes waterproof and impermeable to those chemicals, with the exception ofvarnish solvents, which will presently be described.

The sheet is next immersed in a 20% aqueous solution of normal lead acetate, as a result of which the lead acetate solution enters the openings 2' in the varnish imprint, enters the gelatin coating and diffuses radially into the gelatin coating under the varnish, the extent of radial penetration of the lead acetate solution into the gelatin being indicated by the dotted circles in Fig. 7. The diffusion is slow and proceeds uniformly in all directions. The extent of area panetrated by the lead acetate solution will be determined by the length of time the lead acetate solution is allowed access to the gelatin in the openings 2', and this, in turn, will predetermine the size of the dot or dot units comprising the second tone, to which reference has been made. It is apparent therefore that by controlling the time of immersion of the sheet in the lead acetate solution, any desired tone value for the second tone" in the finished medium can be obtained.

Immediately upon removal of the sheet from the lead acetate solution, the surface thereof is dried by blotting or running the sheet between soft rubber rollers, and the sheet is permitted to become thoroughly dry, after which it is immersed in the following solution:

Parts Water 100 Nitric acid (specific gravity 1.42) 9 Mercurous nitrate As a result of this second immersion, the mercurous nitrate solution also enters the openings 2' in the varnish imprint, enters the gelatin c0at ing and difluses radially into the gelatin coating under the varnish, the extent of radial penetration of the mercurous nitrate solution into the gelatin coating being indicated by the dot-dash circles in Fig. 8. The diffusion is slow and proceeds uniformly in all directions.

Here again, the time of immersion will determine the size of the superimposed dots of mercurous nitrate and accordingly, the value of the "first tone, to which reference has been made.

The superimposed dots must necessarily be smaller than the underlying second tone dots in order to secure a useful difference in the final tone values.

It may also be pointed out that any desired relationship between the first tone" dots and the already established second tone dots can be fixed or determined at this point by control of the duration of immersion.

After the sheet is removed from the mercurous nitrate solution, it is immediately immersed in a 5% aqueous solution of sodium chloride and permitted to remain therein slightly in excess of the immersion period in the mercurous nitrate I solution. The mercurous nitrate in the gelatin in those areas penetrated by the sodium chloride solution. Precipitation of all of the lead acetate to lead chloride may or maynot occur, but at this point it is unnecessary to fix the lead a-cetate in position, since a subsequent treatment which will presently be described, will effectively accomplish this.

After removal of the sheet from the sodium chloride solution, it is again blotted or run through rollers to remove all surface excess of the solution, and is then permitted to become thoroughly dry. I

After the sheet has become thoroughly dry, it is sponged with a solvent for the original varnish imprintin order to remove the varnish. For,

this purpose, anyone of a number of organic solvents may be employed, but the solvent must be one that will not be a solvent for lead acetate, since some lead acetate may, as previously stated, iemain in the gelatin unchanged by the sodium chloride treatment. The mercurous chloride and the lead chloride will not be soluble in any practical varnish solvent. Carbon tetrachloride, benzol, toluol, xylol, butyl alcohol and amyl alcohol are examples of suitable solvents for varnish.

Ethylene glycol monomethyl ether is particularly suitable since it is nontoxic and its vapors are not easily combustible. The varnish is easily wiped clean from the gelatin surface by using soft cotton flannel saturated with the solvent. The sheet, as it appears after removal of the varnish imprint, is shown in Fig. 9.

After removal of the varnish, the sheet is immersed for two minutes in a 10% aqueous solution of sodium sulphate (anhydrous), which changes both the lead acetate and lead chloride to the more insoluble lead sulphate, which becomes permanently fixed within the gelatin.

Thus any lead acetate which was not converted to lead chloride by the sodium chloride treatment is converted into lead sulphate. The sodium sulphate solution apparently has no effect on the mercurous chloride.

The medium now exists as a plain l in film on either a paper or'transparent plastic base. Within the gelatin surface are two white (actinic color) insoluble chemical dot patterns, the one a series of uniformly spaced dots of lead sulphate of a predetermined uniform size, and the other, a. series of dots of mercurous chloride exactly superimposed upon the lead sulphate dots and of a smaller uniform size, the superimposition of one series of dots upon another resulting in an exact registration or proper relative location between the dots.

The medium thus prepared is the medium of the present invention for use in making camera copy. 1

After a suitable drawing, as for example, an ink line drawing has been made upon the medium, one or both of the patterns may be developed in desired areas as a shading or accompaniment of such line drawing.

In order to develop the first tone," a chemical developer composed of 100 parts of water and 1.3 parts of thiourea is applied to the sheet, as by means of a brush, thereby changing the mercurous chloride dots to a black or brown nonactinic color and producing a Ben Day tone of one value, as shown in Fig. 9. In order to defilm will, through double decomposition, be velop the second tone, a chemical developer The lead acetate solution composed of 100 parts of water and 4 parts of sodium sulphide is applied to the sheet, as by means of a brush, thereby changing both the mercurous chloride and lead sulphate dots to a black or brown color and producing a Ben Day tone of a greater value, as shown in Fig. 10.

Instead of using lead sulphate for forming the pattern for the second tone, other actinic colored insoluble chemical compounds which will react with a solution of a soluble sulphide to produce a non-actinic colored compound may be used. Among these are cobaltous tungstate, nickelous phosphate, cupric tungstate, ferric phosphate and thallium tungstate.

I claim:

1. In a method of preparing a medium for use in making camera copy, the steps which consist in impregnating a surface with a chemically-developable pattern comprising spaced dots, and then impregnating said surface with a chemically-developable pattern comprising spaced dots smaller than said first-named dots, said second-named dots being substantially entirely superimposed upon said first-named dots.

2. In a method of preparing a medium for use in making camera copy, the steps which consist in impregnating a surface with chemicals, whose reaction produces a pattern consisting of spaced dots of lead sulphate, impregnating said surface with chemicals whose reaction produces a pattern consisting of spaced dots of mercurous chloride, said second-named dots being smaller than said first-named dots and substantially entirely superimposed upcn the latter.

3. In a method of preparing a medium for use in making camera copy, the steps which consist in applying to a gelatin-coated base sheet an imprint of a water-proof material having uniformly spaced openings therein, and introducing into said openings, in succession, a plurality of chemicals, the reaction of which produces chemically-developable dots in said gelatin, which are exposed, in part at least, through said openings.

4. In a method of reparing a medium for use in making camera copy, the steps which consist in applying to a gelatin-coated base sheet a film of varnish having uniformly spaced openings, therein, immersing said sheet in a lead acetate solution whereby to impregnate the gelain and adjacent said openings with said acetate solution, drying said sheet, and then immersing said sheet in a mercurous nitrate solution, whereby to impregnate the gelatin in said openings with said mercurous nitrate solution.

5. In a method of preparing a medium for use in making camera copy, the steps which consist in applying to a gelatin-coated base sheet a film of varnish having uniformly-spaced openings therein, immersing said sheet in a lead acetate solution whereby to impregnate the gelatine belowsaid openings with said acetate and cause it to diffuse in said gelatin radially of said openings, drying said sheet, immersing said sheet in a mercurous nitrate solution, whereby to cause said nitrate to impregnate the gelatin below said openings and to diffuse radially of the latter, but not to the same extent as the acetate, then immersing the sheet in a sodium chloride solution to change the mercurous nitrate to mercurous chloride and the lead acetate to lead chloride, again drying the sheet, removing the varnish film, and then immersing the sheet in a sodium sulphate solution to change the lead chloride to lead sulphate.

6. A medium for use in preparing camera copy,

said medium consisting of a surface having chemically-developable patterns thereon, one of said patterns consisting of uniformly spaced dots of one substance, and the other of said patterns consisting of uniformly spaced dots of another substance smaller than said first-named dots and superimposed upon the latter.

7. A medium for use in preparing camera copy, said medium consisting of a surface having chemically-developable patterns thereon, one of said patterns consisting of uniformly spaced dots, and the other of said patterns consisting of uniformly spaced dots smaller than said firstnamed dots and superimposed upon the latter, said second-named dots being developable to visibility by means of a chemical, and both of said dots being developable by means of a chemical different than that used for developing said second-named dots to produce a tone of greater value.

8. A medium for use in preparing camera copy, said medium consisting of a surface having chemically-developable patterns thereon, one of said patterns consisting of uniformly spaced dots of lead sulphate, and the other of said patterns consisting of uniformly spaced dots of mercurous chloride superimposed upon and of a smaller size than said first-named dots.

MAURICE D. McINTOSH.

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