US 2670288 A
Description (OCR text may contain errors)
Feb. 23, 1954 Q F, SMlTH 2,670,288
PHOTOGRAPHIC TRACING CLOTH Filed NOV. 30, 1951 I6 EMUL SION 15 GEL A TIN SUB 15 /cELLULosE NITRATE 12 ./-HYDROLIZED PoL YV1NYL- 10 ACE TA TE 11 TRACING CLOTH 14 HYDR oLIzED POL YVIN YL- 1 7 ACE TA TE CELL ULOSE NJTRA TE CELL ULOSE ACE TA TE F1 q. E.'
Z'INULl SION GELA TIN S UB CELL ULOSE NITRA TE' HYDROLIZED POL YVINYLACE TATE CL O TH HYDROLIZED POLYVINYLACETA TE CELLULOSE NITRATE GELA TIN SUB GELA TIN CARL. F. SMITH INVENTOR.
ATTORNEYS Patented Feb. 23, A1954 l UNITEDy STATES PATENT-- 2,670,288 n PHOT'UGRBHIC TRAQG @om "f .l om' Esmee, menester, N. Y., assigner to Ease..
man Kodak Company, Rochester, N. Y., a corporation ol!4 New Jersey Application November so, 1951, serial No. 259,189
(ci. iis-8i 4 Claims. .1
This invention relates to photographic tracing cloth and more particularly to a photographic tracing cloth structure which has substantially improved light transmission without impairment of other desirable characteristics'. l
As is Well understood, photographic tracing cloth is employed, for example, by being exposed to a drawing, or a negative' thereof,'t`o forinan image on the tracing'cl'o'th. Afterproper process'- ing, the tracing cloth may then be employed to print the image ontoI ablue print or other similar copying paper, or the like.
In general, photographic tracing cloth consists of a sheet of sized cloth which is Waterproofed on both sidesto prevent aqueousphotographic solutions rom attacking the sizing of the cloth. a photographic light sensitive layer being coated over one or both of the waterproong layers. Heretofore, the waterproong layer' usually has consisted of a cellulosic material, such as cellulose nitrate, Which material does notV properly adhere to a starch-sized' cloth' withoutv the application of some intermediate subbing' material; When the tracing cloth, after exposure, is treated in aqueous photographic processing solutions even when a subbing material is employed, the waterproofing v layer may' come loose` and permit the water to reach and swell thestarclr sizing of the cloth, thereby making the drawing or tracing on the tracing cloth of no value. Another objection to tracing cloth which is made in this Way' is' that after photographic processing' andi drying ofthe material, the waterproofing layerand its; emulsion sometimes peel or stripfrom the cloth basar f In the Nadeau and' Couch Patent 2,117,814 of May 17, 1938, these diiiiculties are overcome by employing a layer of a mixture of gelatin and cellulose nitrate to the cloth base before the application of the waterproofing, the subbing and photographic emulsion layers.
While photographic tracing cloth made in accordance with this patent is very satisfactory, I have found that it has two undesirable features. It has a rather poor light transmission which results in a low printing speed and on prolonged immersion in aqueous liquids there is a tendency of the Waterproofing layers to curl up and leave the edge of the cloth.
An object, therefore, of the present invention is an improved photographic tracing cloth which includes the desirable features of the tracing cloth described in Patent 2,117,814 and which also has superior light transmission and resistance to aqueous methods.
In accordance with the invention, these and replacing the cellulose nitrateI gelatin subbing layers of Patent 2,117,814 with subbingi layers comprising a hydrolyzed polyvinyl acetatey containing from 27 to 401%.v'inyl acetate. I have found that by employing thesev hydrolyzed polyvinyl acetate layers, the printing speed of the finished product is increased approxirnatelyy 30% and the'edge curl is substantially eliminated. The hydrolyzed polyvinyl acetate kcontaining 27% vinyl acetate is preferred; l
My invention Will be 'further understood by reference to the drawing in which; Fig. 1 is aview in section of one form off atracing cloth madein accordance with [my invention which, except for the novel use of hydrolyzed polyvinyl acetate layers, is similar instructure to that. of4 Patent 2,117,814; and Fig, "21s' a.y quite. similar structure having, however, .a, gelatin coating inthe place of the cellulose` acetate, coating; of Fig.v 1.
In making the photographic `tracing cloth shown in liig. l, a4 solutionv ofrntlie hydrolyzed polyvinyl acetate is applied to both. sides of a calendered, starch-sized-l cloth base. After this solution is dried a solutionofcellul'ose nitrate is applied over both hydrolyzed polyvinyl acetate layers and permitted to dry. n one side'ofthe element thus formed a thin` layer of.A gelatin is' applied and over'this layer. iscoated the light sensitive photographic emulsion.- If the tracing cloth structure shown in Fig. 1` desired, the cellulose' nitrate .layer on. the side opposite the emulsion side may;- be' overcoated withf cellulose acetate; or, if. the structure showneinlFig. 2- is .desired',.,then,instead of the acetate layer a mixed gelatin-cellulose nitrate layer mayk be used over which anr anti-hala'ti'on gelatin coating is placed. The structure of my improved vtracingl cloth may further be apparent by reference to the drawing. In Fig. 1 of the drawing I0 represents a calendered starch-sized tracing cloth. On this cloth base are coated layers ll and l2 of the selected hydrolyzed polyvinyl acetate. The following solution is typical of the one which may be advantageously employed.
Percent Hydrolyzed polyvinyl acetate (27% vinyl acetate) 2 Water 20 Methyl Cellosolve 15 Methyl alcohol 63 other objects may be attained, I have found. by u nitrate.
A suitable composition for the solution employed to coat this layer is the following:
These layers are dried and on one of them is laid a thin gelatin layer I5 which may be coated from the following solution:
Percent Gelatin 1.0 Acetic acid 1.0 v Water 5.0 Methyl alcohol 70.0 Acetone 23.0
The gelatin layer is dried vsomewhat and over it is laid an ordinary gelatine-silver halide emulsion I6.
On the opposite side of the element formed by the application of these layers to the cloth support l0, a layer H of any suitable backing material, such as cellulose acetate.' is coated over the cellulose nitrate layer I4. The cellulose acetate employed may be hydrolyzed cellulose acetate of a precipitation value of 70% and may be coated from an acetone solution. i
Other cellulose organic acid esters such as cellulose acetate propionate could be employed in place of the cellulose acetate layer shown as i1 in the drawing. In making the photographic tracing cloth shown in Fig. 2, a procedure, in general, similar to that employed for making the tracing cloth of Fig. 1 may be followed. A solution of the hydrolyzed polyvinyl acetate is applied to both sides of the calendered, starch-sized cloth base 20. The resulting layers are shown respectively at 2l and 22 on the drawing. After these layers are dried, a solution of cellulose nitrate is applied over both hydrolyzed polyvinyl acetate layers 2l and 22 to form nitrate layers 23 and 24. These nitrate layers are dried and coated with a gelatin subbing coating to produce layers 25 and 2l which are dried. On gelatin layer 25 is coated a light sensitive photographic emulsion 26 as by standard methods. On the opposite layer an additional gelatin layer 28 is coated which prevents curling of the tracing cloth and serves also as an anti-halation layer. The coating compositions employed in connection with the tracing cloth shown in Fig. 1 are satisfactory for employment in making the tracing cloth of Fig. 2.
It is to be understood that this invention is not limited to the exact type of sensitive tracing cloth and the sequence of layers described in the above specification. For example, the support may be any type of suitable cloth or paper which has been sized with materials that swell or dissolve in Water. Other materials may be employed for the waterproofing layer and additional layers of other material may be applied to improve the dry and wet stripping characteristics of the iinished element. I contemplate the use of all modications and equivalents coming within the scope of the vappended claims. The various layers may be coated by any suitable methods known in the art.
I claim: Y
l. A photographic tracing cloth having improved light transmission comprising a sized cloth Base, a layer of hydrolyzed polyvinyl acetate having a vinyl acetate content ci 27 to 40% on each side of the cloth base, a separate layer of cellulose nitrate over each of the hydrolyzed polyvinyl acetate layers, a silver halide emulsion layer attached to one of the cellulose nitrate layers by a gelatin layer, and a cellulose acetate layer over the other of said cellulose nitrate layers.
2. The tracing cloth of claim 1 in which the polyvinyl acetate has a vinyl acetate content of 3. A photographic tracing cloth having improved light transmission comprising a sized cloth base, a layer of hydrolyzed polyvinyl acetate having a vinyl acetate content of 27 to 40% ony each side of the cloth base, a separate layer of cellulose nitrate over each of the hydrolyzed po1yvinyl acetate layers, a silver halide emulsion layer attached to one of the cellulose nitrate layers, and a gelatin layerover the other of said cellulose nitrate layers.
4. The tracing cloth of claim. 3 in which the polyvinyl acetate has a vinyl acetate content of 27%.
CARL F. SMITH.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,117,814 Nadeau et al. May 17, 1938 2,135,524 Nadeau Nov. 8, 1938 2,143,791 Nadeau Jan. 10, 1939 2,350,124 Nadeau et al. May 30, 1944 2,363,764 White Nov. 28, 1944