US 2942975 A
Description (OCR text may contain errors)
United States Patent PHOTOSENSITIVE MATERIAL N Drawing. Filed May 5, 195 5, Ser. No. 506,369
10 Claims. (Cl. 96-7 5) This invention relates to a type of photosensitive material commonly used as an intermediate reproduction material in the drafting art. It can be used to make duplicate tracings from which additional prints can be made by the ordinary reproduction methods. The particular type of material to which the invention relates is made by coating a suitable light transmitting base such as tracing cloth, tracing paper and other transparentized bases or naturally transparent or translucent bases with a colloid layer containing a silver halide and an agent capable of hardening a colloid under the influence of light. The base for this type of photosensitive material may for example be tracing cloth which has been coated with a lacquer to make it waterproof, then coated with a subbing layer and finally coated with the light sensitive layer described above. The purpose of the subbing layer is to promote adhesion between the light sensitive layer and the waterproofed base material. The substratum also afiects some characteristics of the sensitive layer, such as printing speed, gradation .(contrast keeping .quality, .etc.
Photosensitive materials of the type described are'exposed to light under anegative original which may be a brownprint made from a tracing or a drawing on transparent paper. After exposure, the material is washed with water to remove thecolloid layer -from the unexposed areas and then developed with :a photographic developing solution to form a metallic. silver relief image of the exposed areas which usually appears black; v
For the most part, chromates have been used as the light sensitive hardening agent for the colloid in the photosensitive material of this type known in the art. However, Patent No. 2,663,640, which issued to M. K. Reichel and W. Neugebauer on December 22, 1953, discloses the use of diazido compounds as the light hardening agent in this type of material.
The subbing layer used in this type of material includes a protein colloid such as glue, gelatin and the like. It has been a practice to add a small amount of formaldehyde to increase the water resistance of the colloid and thereby improve the adhesion of the photosensitive layer to the base during the processing of the material to form the image thereon. Despite the use of this formaldehyde, one of the most effective colloid hardening agents known, it has been found that the adhesion of the photosensitive layer varies considerably from batch to batch in production which has been a great handicap in the commerical use of this type of reproduction material. In addition, the formaldehyde is objectionable because of its unpleasant odor.
Now it has been found that improved results are obtained by eliminating formaldehyde from the subbing and using a small amount of zirconium salt. The zirconium salt may either be used in a solution which is applied to the subbing layer or the zirconium salt may be incorporated with the protein colloid and coated on the base material therewith to form the subbing layer.
The principal objects of the present invention are to 2,942,915 Patented June 28, 1960 2 improve intermediate reproduction materials having a light sensitive layer including a colloid, a silver halide and a light-hardening agent by using a zirconium salt carried by the subbing for such layers and eliminating the objectionable effects resulting from the use of formaldehyde in such materials.
The principal zirconium salt which has found use according to the present invention is zirconium acetate having the approximate formula H ZrO (C H O However, other zirconium salt may be used such as zirconium oxychloride Zr O CI .6H O ammonium zirconyl carbonate, (NH ZrOH(CO .2H O and zirconium sulphate, Zr(SO .4I-I O. When some of these salts are used, it may be necessary to adjust the pH. The best results are obtained if the pH of the wash solution containing the zirconium salt is adjusted to fall within a range close to the isoelectric point of the colloid used. In the case of a particular gelatin suitable for use in subbing layers, the pH of the wash solution used therewith should be between 4 and 6. It is also necessary to balance the ratio between the water and organic solvent used in the wash solution since if the percentage of organic solvents is toogreat, the zirconium salt may tend to separate out in the form of a gel. I
The protein colloids which are useful in the subbing of the present invention are gelatin, glue, albumin, casein and zein.
The waterproofed layer which is applied to protect the tracing cloth may be a nitrocellulose lacquer or other types of lacquers may be used. A wide variety of resins may be incorporated in the waterproofed layer or multiple resin coats may be used such as vinyl resin coating followed by nitrocellulose both of which together may be considered to be the waterproofed layer. it is also C? tomary to apply wateiproofed layers to the back side of the material. Additional layers may also be applied to the back side in ,order to make the properties of this sidesimiliar to those of thephotosensitiye side of the material in order to prevent curling.
' The practice of the' invent-ion'is illustrated by thejfollowing examples:
' Example I A waterproofedtracing cloth was coated with a subbing layer of the following formula:
grams gelatin 8800 cc. methyl alcohol 1600 cc. glacial acetic acid 100 cc. Water Ethyl alcohol and/or acetone may replace all or part of the methyl alcohol in the above formula. Before coating the photosensitive layer on this subbing it was treated with a wash solution made up according to the following formula:
20 cc. zirconium acetate solution (this solution contains the equivalent of 14% ZIO2) 350 cc. water 600 cc. organic solvents selected from methyl alcohol,
ethyl alcohol, acetone and methyl ethyl ketone Small percentages of wetting agents and flow agents may also be incorporated in this formula.
The material was then coated with a light sensitive coating made up according to the following formula:
To an emulsion consisting of:
- oz. by weight of potassium chloride in distilled water Example II A tracing cloth provided with a waterproofed lacquered coating was coated with a snubbing layer made according to the following formula:
120 grams gelatin 9500 cc. methyl alcohol 1500 cc. glacial acetic acid 150 cc. water 120 cc. zirconium acetate solution containing the equivalent of 14% Zr Ethyl alcohol, acetone and methyl ethyl ketone may be used to replace all or part of the methyl alcohol in the above formula. Small quantities of wetting agents or flow agents may also be added to this subbing solution.
The base material provided with this subbing was coated with the same photosensitive material described in Example I and reproductions made with the material showed the same excellent properties and in particular, the same outstanding adhesion of the image areas to the Example Ill The waterproofed tracing cloth material subbed in accord with Example II was coated with a light sensitive composition exactly the same as that disclosed in Example I except that 2 oz. by weight of 4,4'-diazido-sti1- 7 bone, 2,2-disulfonic acid sodium salt dissolved in 10 liquid ounces of distilled water were substituted for potassium'bichromate solution used in Example I.
' Reproductions made with this material exhibited greater adhesion of the image areas to the base than relief image comprising a base, a subbing layer including gelatin and a zirconium'salt on said base, a light sensitive emulsion layer including a silver halide, photographic glue, and a light hardening agent selected from the group of dichromates and diazido compounds, said light sensitive layer being coated on said subbing layer whereby when the light sensitive layer is exposed to light the exposed portions of said light sensitive layer adhere securely to the subbing layer.
2. The invention according to claim 1 in which the base is of light transmitting material.
3. The invention according to claim 2 in which a waterproofing layer is provided on the base.
4. The invention according to claim 3 in which the waterproofing layer is nitrocellulose, the base is tracing cloth, the zirconium salt is zirconium acetate, and the hardening agent is a bichromate.
5. The invention according to claim 1 in which the hardening agent is a bichromate.
6. The invention according to claim 1 in which the hardeningagent is a salt of 4,4'-diazido-stilbene, 2,2- disulfonic acid. I
7. The invention according to claim 1 in which the subbing layer-has a pH of 4 to 7.
8. The invention according to claim 1- in which the pHlof the, subbing layer falls close to the isoelectric point of the gelatin.
. 9. The invention according to claim 1 in which the zirconium salt is applied by a wash to the subbing layer. 10. The invention according to claim 1 in whichthe zirconium salt is incorporated in the subbing layer prior to coatingon the base.
References Cited in the file of this patent UNITED STATES PATENTS 2,327,004
OTHER REFERENCES Journal of Photography, May 25, 1951, pages 267 and 268, V01. XCYHI, NO; 47491. i i V