US 3505066 A
Description (OCR text may contain errors)
April 7, 1970 J, M. P s 3,505,066
. PHOTOGRAPHIC PRINT-OUT PROCESS UTILIZING BINDER-FREE SILVER FLUORIDE Filed Oct. 5. 1966 2% x -SUPPORT L X L 267" ,7 ,7/ yyyyyyyyyyyy 22 J I, 1/ I, ll I I 1' 1 1 1 1 r 1 HG IIIIIIIIIIII VACUUM DEPOSITION OF GOLD IIIIIIIIIIII VACUUM DEPOSITION OF SILVER 26 PHOTOSENSITIVE STRATUM I I I I I I I I I I I I l IIl r glLeER BF3 VAPOR FLUORIDE FIG 2 osve LOPED NEGATIVE EXPQSED AREAS FROM EXPQSURE TO LIGHT CONTAINING ULTRAVIOLET RADIATION INVENTOR.
Guam and M and ArrorInsvs United States Patent 3,505,066 PHOTOGRAPHIC PRINT-OUT PROCESS UTILIZ- ING BINDER-FREE SILVER FLUORIDE Joel M. Peisach, Hudson, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed Oct. 5, 1966, Ser. No. 584,447 Int. Cl. G03c 1/02 US. C]. 9627 5 Claims ABSTRACT OF THE DISCLOSURE Print-out images may be obtained by exposure of silver fluoride strata to ultraviolet radiation. The silver fluoride stratum is preferably prepared by BF treatment of vacuum deposited silver. The print-out image density may be increased by heating after exposure.
The present invention relates to novel photographic processes, and more particularly to the formation of photographic images by print-out processes. The primary object of the present invention is to provide a print-out process employing a photosensitive element comprising photographic materials formed at least in part by the vapor fluorination of silver coated substrates.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection withthe accompanying drawings wherein:
FIGURE 1 shows successive diagrammatic cross-sectional views of the preparation of typical photosensitive elements utilizable in the present invention, said elements being prepared for example by the process described and claimed in the copending application of Paul D. Lubin and Joel M. Peisach, Ser. No. 584,412, filed concurrently herewith.
FIG. 2 shows an exaggerated cross-sectional view of an element prepared by a process such as that described in FIGURE 1 being used in accordance with the present invention.
The silver halide substrates that are utilized in the process of the present invention are unique and different from the prior art in that they contain some form of a silver fluoride as part of the photosensitive material. Heretofore, the photographic art had generally considered silver fluorides to be light insensitive and, therefore, of no importance in photography. Reference is made to Light- Sensitive Systems, by Jaromir Kosar, published 1965 by John Wiley & Sons, Inc., New York, NY. Particular reference is made to pages 18 and 19. Silver fluoride is known to exist in three forms, namely AgF, Ag F and AgF All of these are water soluble. See the 41st edition of the Handbook of Chemistry and Physics published by the Chemical Rubber Company, at page 648. The existence of other forms or complexes of silver and fluorine are not known and can only be theorized. It is because of this water solubility factor that silver fluoride was not utilized in the prior art to prepare a silver halide emulsion by the techniques usually employed with the other silver halides. It is seen, therefore, that the ability to prepare such photosensitive silver fluoride strata and the utilization of these photosensitive strata to obtain a photographic image would, indeed, be unique and unexpected.
In view of the fact that the known forms of silver fluoride are water soluble, it seems apparent that the silver fluoride photosensitive elements to be utilized in the present invention must be prepared in a manner wherein water is excluded.
The silver fluoride photosensitive elements utilized in the present invention are best prepared by the deposition of metallic silver upon a support followed by contracting the silver coated support with boron trifiuoride vapors. Particularly beneficial strata for utilization in the present process are those wherein the silver is vacuum deposited, i.e., by evaporation or sputtering techniques.
A photosensitive element that gives rise to excellent results in the present invention is one wherein gold is vacuum deposited in conjunction with the vapor deposition of the silver prior to the boron trifluoride vapor treatment.
A suitable vacuum deposition process is described in United States Patent No. 3,142,566 to Edwin H. Land, granted July 28, 1964. Apparatuses necessary to prepare such products are well-known in the art. A typical example of such a machine is described in the book Vacuum Deposition of Thin Films, by L. Holland, published by John Wiley & Sons, Inc., New York, N.Y., 1948, pp. 7 and 8.
Photosensitive elements utilizable in the present invention may be prepared on a variety of substrates. These support materials include any suitable paper such as baryta paper or any suitable plastic such as polyethylene terephthalate sold under the trade name Mylar or Cronar by E. I. du Pont de Nemours & Company, Wilmington, Del. Cronar is believed to be polyethylene terephthalate subcoated with what is described as a water permeable colloidal layer such as is set forth in United States Patent Nos. 2,627,088 and 2,698,242. As is known in the art, subbing layers may be provided for a multitude of purposes. Methods for preparing such subbing layers on base materials are well known and need not be described herein.
Photosensitive strata containing silver fluoride can be developed to a negative silver image by exposure of the photosensitive stratum to a light source containing ultraviolet radiation. Typical light sources that contain such UV radiation are a xenon lamp and conventional photoflood lights which are generally available in commerce. The process of the present invention utilizes print-out exposure techniques. In this process the image forming subject is placed in contact with the photosensitive stratum and a photo exposure is made. Subsequent to the exposure, an image will appear. It is thus seen that wet development of the photo exposed stratum is unnecessary. Ofttimes, heat can be utilized in conjunction with the light to intensify the image.
The process of the present invention gives rise to a high resolution material with low speed and as such can be utilized in stellar photography.
The following examples are set forth to illustrate this invention and are not intended to be limiting.
The subject matter set forth in Examples I and II is claimed in Ser. No. 584,412.
EXAMPLE I FIGURE 1 illustrates the production of a photosensitive element utilizable in the present invention. Gold was vacuum deposited by being evaporated uniformly onto a sheet of nnsubbed Mylar approximately 0.014 inch thick, 4% inches wide and 15 inches long to form a gold stratum 22 with a coverage of approximately 10 mg. per square foot. Then silver was vacuum deposited by being evaporated onto the support coated with gold to form a gold and silver stratum 24, with a coverage of about 60 mg. per square foot of silver.
This sheet was then placed in a desiccator which was then evacuated at room temperature. The vacuum was broken by the introduction of 9 liters of boron trifluoride gas (equal to 27 grams of B1 at room temperature and atmospheric pressure). The sheet was left in the boron trifluoride atmosphere for 20 hours. The so treated sheet was translucent indicating the formation of a silver fluoride photosensitive stratum 26.
EXAMPLE 11 Silver was vacuum deposited by evaporation onto a sheet of Cronar film to provide a stratum having a silver coverage of approximately 20 mg. per square foot. This sheet was placed in a desiccator which was then evacuated at room temperature. The vacuum was broken by the introduction of boron trifiuoride gas into the system. The sheet was left in this BF atmosphere for six hours. The sheet became translucent indicating the formation of a silver fluoride.
EXAMPLE III A photosensitive element comprising silver fluoride on baryta paper was exposed to a light source containing UV radiation for approximately 2 minutes. Upon removal of the light source the image formed from a high contrast object became visible.
EXAMPLE IV A photosensitive element comprising silver fluoride on a substrate of Mylar was exposed to a Number 2 Westinghouse Photoflood for approximately one minute. This element was then subjected to heat within the range of 80 F. to 180 F. for about minutes to intensity the previously formed image obtained from a conventional step-wedge.
EXAMPLE V A photosensitive element containing silver fluoride was exposed to long-wave ultraviolet radiation from a Model X4 Blak Ray made by the Ultraviolet Products Company, Incorporated, San Gabriel, Calif., for one minute at a distance of 2 inches. An image of moderate accutance became visible immediately upon removal of the light source.
Photosensitive materials utilized in accordance with this invention are characterized by negligible grain, relatively low sensitivity, e.g., an exposure index of less than ASA 1 and by the formation of images exhibiting long soft or low contrast, curves.
It will be readily appreciated, that the binder-free silver fluoride photosensitive element should be prepared by a process wherein substantially no water is present, in view of the previously discussed fact of silver fluoride solubility in the Water. Typical reagents that can be utilized to fluorinate silver include H-F, F and B1 The advantages to be derived from the use of the boron trifiuoride,
in the vapor state as opposed to the HF and F gases include easy availability in commerce, relative ease of handling, the relative freedom from toxicity, and the ability to use conventional reaction vessels.
The term binder-free is utilized to signify the fact that the photosensitive elements used in the present invention are prepared without gelatin or an equivalent binder as is used in conventional photographic materials. In certain instances, however, it may be desirable to apply a stratum of a polymeric material over the surface of the binderfree photosensitive element, in which event the silver fluoride will still be substantially binder-free.
Since certain changes may be made in the above process without departing from the scope of the. invention herein involved it is intended that all matter contained in the above description and accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
What is claimed is:
1. The process of forming a visible image comprising exposing a binder-free stratum of silver fluoride to ultraviolet radiation until a print-out image is formed, said silver fluoride stratum having been prepared by fluoridation of vacuum deposited silver.
2-. The process of claim 1 wherein said vacuum deposited silver was deposited on a stratum of vacuum deposited gold.
3. The process of claim 1 wherein said photosensitive stratum is subjected to heat subsequent to said photo exposure.
4. The process of forming a visible image which comprises exposing a photosensitive element to a light source containing ultraviolet light, said photosensitive element having been prepared by the reaction of boron trifiuoride with silver, said silver having been vacuum coated on a support, and heating the photo exposed element within the range of F. to F., subsequent to said exposure, to intensify the image.
5. The process of claim 4 wherein the silver coated substrate further ctontains metallic gold.
References Cited UNITED STATES PATENTS 1,5 60,240 11/ 1925 Jelley 96-94 3,142,566 7/1964 Land 9694 3,142,567 7/1964 Morse 96-94 FOREIGN PATENTS 547,806 9/1942 Great Britain.
J. TRAVIS BROWN, Primary Examiner US. Cl. X.R.