US2544877A - Bichromate sensitized photographic materials - Google Patents

Description

Patented Mar. 13, 1951 BICHROMATE SENSITIZED PHOTOGRAPHIC MATERIALS Robert S. Bryce, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey No Drawing. Application May 3, 1947, Serial No. 745,734

1 Claim. 1

This invention relates to the preparation of sensitive photographic materials and particularly to bichromate sensitized photographic materials.

In Staehle U. S. application Serial No. 558,346, filed October 12, 1944, a process is described for the preparation of photographic reversal images in a layer of bichromated hydrophilic colloid such as gelatin or glue containing an aqueous dispersion of a water-insoluble, soft, synthetic resin capable of drying to a continuous film when the dispersion is coated on glass. Bichromated gelatin or glue sensitive layers are well known and when a dispersion of a soft, synthetic resin is added to such layers, a material suitable for the formation of reversal images is obtained. Resin dispersions which may be used for this purpose are aqueous dispersions of an acrylate resin such as polymethyl acrylate and polyethyl acrylate, a polystyrene dispersion, a polyvinyl acetate dispersion and neoprene latex. A dispersion of plasticized cellulose nitrate in water may also be employed. The mixture may also contain a wetting or dispersing agent such as a sodium alkyl sulfate or a polyethylene glycol and a plasticizing agent such as glycerol or ethylene glycol. The sensitive layer maycontain white pigments such as titanium dioxide or 001- cred oxidizers such as carbon black, cobalt blue or yellow ochre.

The material described in Staehle application, Ser. No. 558,346 is suitable for coating on glass, metal, plastics, rubber, etc., to form light-sensitive coatings in which a reversal image may be formed by washing away the exposed portions of the layer. One disadvantage of this process is that the exposed areas sometimes cling tenacious- 1y to the support on which the sensitive layer is coated and cannot be washed away to form a clean image, without the use of an abrasive. This is especially true of the sensitive material of Staehle application Ser. No. 558,346 containing titanium dioxide or other pigments, or containing dyes as described in Staehle application Ser. No. 745,736, filed May 3, 1947.

It is therefore an object of the present invention to provide a bichromate sensitized colloidal material which can be used to form sensitive coatings, the desired areas of which are readily removable from the support on which they are coated. A further object is to provide a bichromate sensitized hydrophilic colloid material containing an aqueous dispersion of a soft, synthetic resin and also containing a material which will permit a clean breakaway of the exposed portions from the support on which the material is 2 coated. Other objects will appear from the following description of my invention.

These objects are accomplished by incorporating in the bichromated sensitized hydrophilic colloid a water-soluble phosphate, such as an alkali metal or ammonium phosphate.

According to the preferred embodiment of my invention, a solution of sodium hexametaphosphate or other phosphate and pigment are mixed in a ball mill, and a gelatin solution, acrylate resin dispersion, such as polymethyl acrylate or polyethyl acrylate, and sensitizer such as ammonium or potassium bichromate are added. The mixture is then further ball mixed to mix the ingredients.

The sensitized material produced in this way may be coated immediately on a support by spraying, brushing or other suitable manner of application or the sensitive mixture may be stirred for extended periods of time prior to coating.

Before the sensitive material is coated on the support, it is generally desirable to coat the support with a primer. Numerous materials are available for this purpose. In some instances, the support may be rubbed with turpentine to produce a prime coat or various synthetic resin or cellulose ester primers may be used. A satisfactory primer is a solution of polyvinyl butyral in ethyl alcohol, isopropyl alcohol and Cellosolve ethylene glycol ethyl ether. Other suitable primers are solutions of phenol-formaldehyde, urea-formaldehyde, unmodified phenolic resin, ethyl cellulose, and half-second cellulose nitrate.

My invention will now be described by reference to the following specific example.

A sensitive material capable of producing a blue reversal image is produced by adding the following to a ball mill and grinding for 48 hours.

A. Ultramarine Blue grams 40 Water cc Sodium hexametaphosphate (50% solution) cc 15 The following ingredients are mixed for adding to (A) in the ball mill.

B. Polymethyl-polyethyl acrylate (50% dispersion) cc 1'75 Water cc Gelatin (25% solution) cc 300 Ammonium bichromate (20% solution) cc 50 The mixture is agitated in the ball mill for 30 minutes and this completes the preparation.

The sensitive material is used by spraying onto a support primed with one of the primers described above. In some instances the primer is unnecessary as, for example, where the sensitive material is coated on a polystyrene support. After coating the sensitive material on the support, it is exposed through a positive to a high intensity light and is then placed in-warm water or in warm water to which a small amount, for example, 1% of ammonium hydroxide has been added for a few seconds to swell the exposed areas. The exposed layer is then washed with a stream of warm water for a few seconds to remove the swollen areas. The layer now exhibits a blue positive image and is dried and coated if desired with a transparent lacquer or enamel to protect the finished image.

Various pigments other than Ultramarine Blue may be used to color the sensitive material. For

example, the following pigments may be used:

Fast Pigment Yellow (o-amino-p-sulfobenzoic acid and 1 phenyl 3 methyl-5-pyrazolone) Chrome Yellow D (13-naphthylaminemonosulfonic acid bromine and salicylic acid), Carbanthrene Red BNV (Color Index No. 1162), Carbanthrene Blue GCD (Color Index No. 1113), Carbanthrene Yellow G (Color Index No. 1118 and Lithosol Red CSP (Color Index No. 165).

While I prefer to use the water-soluble phosphates of my invention with a .bichromate sensitized colloid containing an aqueous dispersion of a synthetic resin to form a positive image, it is also possible and advantageous to use waterscluble phosphates with an ordinary bichromate hydrophilic colloid such as bichromated gelatin in order to improve breakaway. In either case the. Water-soluble phosphate is added to the gelatin or other colloid in amounts which may vary over. wide limits, for example, from 0.5 to 200% of the amount of gelatin in the sensitive mixture. Inaddition to the useof the colored sensitive materials for the production of. monochrome and polychrome line images, it has been found possible to make full colored pictorial images using three primary colored sensitive materials, by either the halftone or continuous tone process.

In order to make a halftone full colored reproduction, halft'one transparent negatives are prepared of the three primary colors by any of several well-known means. Halftone transparent positives are prepared from the negatives by either contact or projection printing followed by normal photographic processing. A white support is then primed and any of the colored sensitive materials such as the red is coated on it.

The red coated plate is then exposed to light 5 throughthe red separation positive. The exposed plate isprocessed and dried as described in the example above, except that no protective layer is coated on the finished image. The red image is then overcoated with a primer or the second priming may be omitted, and the blue sensitive material is sprayed on the plate. The plate is then exposed to light through the separation positive in register with the red image and the plate processed and dried as before. The plate is again primed if desired and coated with the yellow sensitive material. It is then exposed to the yellow separation positive in register with the red and blue images. It is processed and dried as before to produce a complete full colored picture. If desired, it may be coated with a transparent protective overcoat or a black key image can be added to it by the use of a black sensitive coating and processing.

A continuous tone full-colored picture can be made in the same manner as a halftone picture using continuous tone separation .positives. However, since some of the pigments are of an opaque nature, it is preferable to use transparent colored dyes or pigments for this purpose.

It will be understood that the examples and modifications described herein are illustrative only and that my invention is to be taken as limited only by the scope of the appended claim.

What I claim is:

A light-sensitive coating composition comprising a. mixture of a bichromated gelatin, an aqueous dispersion of a water-insoluble soft synthetic resincapable of drying to a continuous film when thedispersion alone is coated onglass and said resinbeing selected from the group consisting of acrylate, styrene, vinyl ester and neoprene resins, a, pigment and sodium hexametaphosphate.

ROBERT S. BRYCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,981,102 Hagedorn Nov. 20, 1934 2,184,319 Heigs Dec. 26, 1938 2,239,284 Draisbach Apr. 22, 1941 2,256,390 Hewitson Sept. 16, 1941 2,376,005 Potter May 15, 1945 2,476,527 Barnes July 19, 1949 FOREIGN PATENTS Number Country Date 228,377 Great Britain Feb. 5, 1925 573,771 Great Britain Dec. 5, 1945