US3157510A

US3157510A - Silver-resin print paper

Info

Publication number: US3157510A
Application number: US184562A
Authority: US
Inventors: Charles F Amering; Edward C Yackel
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1962-04-02
Filing date: 1962-04-02
Publication date: 1964-11-17
Anticipated expiration: 1981-11-17

Description

United States Patent Ofi 3,157,510 Patented Nov. 17,1964

ice

3,157,510 SEVER-RESIN PRINT PAPER Charies F. Amering and Edward C. Yaclrel, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Apr. 2, 1962, Ser. No. 184,562 7 tllaims. (Cl. 96-114) This invention relates to photography and particularl to a method and material for preparing stable silver photographic images.

It is well known to prepare silver photographic images by exposure and processing of developing-out materials in which the photosensitive agent is silver halide, dispersed in gelatin coated on a suitable support like paper, transparent film, glass or metal. When such materials are used, the silver image is produced in the gelatin layer.

Gelatin is an excellent dispersant and vehicle for preparing silver halide emulsions and being water permeable facilitates processing with aqueous solutions.

Unfortunately, gelatin also has several shortcomings. It is hygroscopic, subject to attack by microorganisms, mites, cockroaches, etc. It changes in flexibility With temperature, humidity, and aging. It is ditiicult to completely remove emulsion addenda, residual silver salts, and processing chemicals from gelatin coatings. These in time, especially at high relative humidity and temperature, may decompose and cause background stain, image toning or fading, and mottle.

One object of the invention is to provide a photographic material, which has the benefit of the presence of gelatin during the preparation and coating of the emulsion and the development of the silver image, and the advantage of the absence of gelatin in the finished photograph.

Another object of the invention is to provide a photographic element from which a silver halide photographic print may be obtained having physical characteristics which do not change with temperature or humidity.

A further object of the invention is to obtain photographic prints which are pliable, resistant to abrasion and cracking, and to attack by microorganisms, mites, cockroaches, etc. Other objects of the invention will appear herein.

These objects are achieved by the use of a photographic s lver halide element in which the matrix or carrier for the silver salt consists substantially of a dispersion of about 60 to 95 percent by weight of minute particles of a water-insoluble soft acrylate polymer resin in a continuum of about to 40 percent by weight of unhardened gelatin.

After the photographic element has been exposed and processed in a conventional manner, it may conveniently be washed in warm water at 90 to 150 F. This treatment dissolves and removes the gelatin and enables the resin particles to coalesce in a thin continuous layer which adheres strongly to the support and entraps and retains the image silver. The resin layer is flexible, resistant to cracking and abrasion, and presents a surface sufiiciently smooth and glossy to obviate ferrotyping.

The gelatin used in the preparation of our photosensitive layers, both for precipitating the silver halide and as the film-forming binder, is of low jelly strength, preferably below 100 grams Shoom, the optimum value being about 50 grams Shoom. Glues such as fish glue and gums such as gum arabic, may be employed instead of or in addition to the gelatin. Gelatins used in the preparation of conventional photographic emulsions have a Shoom value above 200 grams.

The Water-insoluble acrylate resins useful in this invention comprse acrylate polymers, for example homopolymers of methyl acrylate, ethyl acrylate, isopropyl acryalte,

n-propyl acrylate, n-bntyl acrylate and isobutyl acrylate and their copolymers with acrylonitrile. The level of aorylonitrile units in the resin should be not more than about percent of the total weight of the monomer units. The acrylate polymers are used in the form of latices or resin hydrosols having not more than about 50 percent solids content (resin hydrosols containing higher proportions of solids are less stable and tend to precipitate some of the resin). Resins of the preferred type are soft, that is, the resin particles tend to coalesce to form a continuous film when coated on a support and dried. The presence of gelatin and the surfactant used in forming the hydrosol prevents the resin from coalescing when the photographic emulsions coatings are dried in manufacture.

The physical characteristics of the finished product can be varied considerably by selection of the resin for use in the photographic elements of our invention. If a slightly adhesive surface is wanted for example to facilitate mounting a positive transparency on a glass slide, a soft resin with a relatively high ratio of alkyl acrylate to acrylonitrile can be used. If an abrasion-resistant final product is desirable, the use of a higher ratio of acrylonitrile results in a harder print.

Resin to gelatin ratios (dry weight) useful in this invention range from :40 to 95:5 (resin to gelatin) with the preferred range from resin:30% gelatin to 99% resin: 10% gelatin. When a layer representing this combination is washed after processing in warm to hot water (at temperatures between about to F. for about 30 seconds or longer depending on the temperature of the wash water, pressure applied, compositions used, etc.), the gelatin is eliminated thus leaving the coalesced resin film containing the developed silver image on the support.

Developing agents can be incorporated in the photographic emulsion if desired but they must be selected from compounds that do not tan gelatin, under the processing conditions to be used. 7

The emulsion can be coated on a variety of supports, for example, glass, transparent film like cellulose ester, polyolefins, polyester, etc., fiber glass, translucentized paper, baryta-coated paper, waterproof paper, etc. The support should be free of hardening agent which might otherwise wander into the emulsions and harden the gelatin.

The ratio of silver to the gelatin-resin vehicle is not critical but we find that a proportion of about one mole of silver halide to about 250 to 400 grams of the gelatin-resin is preferable, as lower ratios tend to retard processing and higher ratios tend to give images of poor quality.

The most useful pH range for our silver halide, gelatin, resin hydrosol compositions when coat ng onto a support is from about 5.0 to 7.0.

During processing of the'latent image, after exposure, the exposed silver halide is converted to metallic silver and the residual silver halide is removed by conventional nonhardening fixing techniques. The processed material is washed in warm to hot water of about 90 to 150 F. to remove the gelatin.

The following examples illustrate but do not limit our invention.

Example 1 To a liquefied and stirred silver halide gelatin emulsion at 40 C. containing one mole of a silver bromoiodide (80 mol percent of the halide being bromide) and 20 grams of gelatin with a jelly strength of 50 grams Shoom, were added 300 grams of 50% aqueous dispersion of a water-insoluble soft resin which resin comprises essentially a copolymer of 75% methylacrylate and 25% acylonitrile units by Weight. To this were added 400 grams of water and 500 grams of a 20% aqueous solution of a low-grade gelatin having a value of 50 grams Shoom. (The gelatin used was soluble in water at room temperature.) This mixture was coated on 112 pound paper stock to give 0.4 gram of solids per square foot and dried.

A sample of the above coating was exposed through a' photographic negative and processed in Kodak Developer D72, diluted 1:1, for two minutes, bathed in 1 percent 1 acetic acid stop bath for 15 seconds, fixed in Kodak fixing bath F-24 for 4 minutes, washed in water at 100 F. for 2 minutes, and dried. a

The dried photographic prints were noncurling, had

excellent flexibility, and were resistant to abrasion. The

Example 2; I

The emulsion of Example 1; was used with the exception that the soft resin dispersion consisted of solids made from 90% ethylacrylate and acrylonitrile. The emulsion was coated on'a subbed film support of cellulose acetate. The emulsion coating was exposed through a photographic negative and processed to a positive by the The positive was fixed in Kodak fixing bath F-24 for four minutes, and transferred to a water wash. All steps were carried out at room temperature of 70.

The positive while still wet was washed for 2 minutes in wash water at 100 F. and was then squeezed into contact with a glass plate as a lantern slide. The processed and mounted lantern slide showed reduced fading in the highlight areas when compared to a similarly processed control which was also mounted on glass. The print made from the resin containing emulsion prior to being mounted on glass was tacky and if left unmounted would have abraded easily or would have retained any fingerprints, dirt, or lint which came into contact with it because of this tackiness.

I Example 3' I To a liquefied and stirred silver halide gelatin emulsion at 40 'C. containing one mole of silver chloride and 2-0 grams of a photographic grade of gelatin having a Shoonr value of 43 grains, were added 280 grams of an aqueous dispersion of polymethylacrylate (47% solids). To. this was added a solution containing 500 cc. of water and 300 grams of a 20% solution of a photographic gelatinhaving ,a Shoom value of' 43 grams. This mixture was coated to give 0.5 gram of solids, per square foot and dried.

This coating was exposed and processed as in Example 1. The dried print was noncurling, flexible, resistant to Y abrasion and had a surface gloss equivalent to a ferro typed print. a This print was subjected to exposure on a shelf in an open-sided, roofed enclosure in Panamajtropicalconditions) for three months along with a conventional photographic paper print prepared by conventional procedures. The results indicated that the acrylate-resin containing print did not turn brown, the highlights remained at full density and the print did not pitfrom the tone,reduced highlights and surface pitting from fungus growthi 7 growth of fungi. The control print exhibited a warmer 4 Example 4 The coating was exposed to a line negative and processed in Kodak Developer D ll for 2 minutes, rinsed in Kodak stop bath SB-la for 10 seconds and fixed in Kodak fixing bath 1 -24 for 4 minutes. The line print was then washed in warm water at 120 F. for 2 minutes and dried. The print was noncurling, and was resistant to abrasion. The print was subjected to exposure on a shelf in Panama for 3 months as in Example 3. N0 stain or reduction in highlight density was noted. This was compared to the same control coating used in Example'3. This experiental coating did not pit from the growth of fungi.

Example 5 V The emulsion in Example 3 was used except the solids in the resin dispersion used as par-t of the colloid consisted of 60% isopropyl-acrylate and 40% acrylom'trile. The coating was processed as in Example 1. The dried print was noncurling, had excellent flexibility and was very resistant to abrasion. The surface gloss was at least equal to a ferrotyped print. I

Aprint made from this coating. was subjected to exposure for 3 months in Panama as in Example .3. No stain nor reduction in highlight densityv was noted. The amount of fungi that was on the surface was about equal to the experimental coatings in Examples 3 and 4 and again showed no surface pitting from the growth of fungi. I V

The advantages of our material over prior art materials are now apparent. The products of our invention reducethe problems due to'fingerprints, smudges, accition. They are :also free from attack by microogranisms, mites, etc. I

The photographic emulsions used in practicing our invention are of the developing-out type. They can be chemically sensitized by any of the well-known chemical sensitizers by any of the accepted procedures. The.

emulsions may also be optically sensitized providing the sensitizing dyes do not react with or dissolve in the polymer to give colors or stain. The emulsions can containv stabilizing agents if desired.

We claim:

1. 'A photographic element from which photographic prints resistant to tropical conditions may be prepared which comprises a support bearing a layer comprising photosensitive silver halide and a vehicle therefor com-I posed of about 60-95% by weight of a water-insoluble resin selected from the group consisting of the homopolymers of alkyl acrylates, the 'alkyl being 1-4carbon atoms and their copolymers with ac'rylonitrile in which the level of the acrylonitrile units is no more than about 50% of the total'weight of the monomer units dispersed in unhardened, low jelly strength gelatin of less than grams Shoom jelly strength. I

2. A photographic element'from which photographic prints resitant to tropical conditions may be prepared which comprises a support bearing a layer of photosensitive silver halide and ,a vehicle therefor composed of about 60-95% by weight 'of a water-insoluble resinof 50-100% alkyl acrylate, which resin is dispersed in unhardened, low jelly strength gelatin of less than 100 grams Shoom jelly strength.

3. A photographic element from which photographic prints resistant to tropical conditions may be prepared which comprises a support bearing a layer of photosensitive silver halide and a vehicle therefor Composed of about 6095% by weight of a methyl acrylate-acrylonitrile resin, the acrylate comprising at least 50% thereof which resin is dispersed in unhardened, low jelly strength gelatin of less than 100 grams Shoom jelly strength.

4. A photographic element from which photographic prints resistant to tropical conditions may be prepared which comprises a support bearing a layer of a photosensitive silver halide and a vehicle therefor composed of about 60-95% by weight of polymethyl acrylate resin dispersed in unhardened, low jelly strength gelatin of less than 100 grams Shoom jelly strength.

5. A photographic element from which photographic prints resistant to tropical conditions may be prepared which comprises a paper support bearing a layer of photosensitive silver halide and a vehicle therefor composed of approximately 88% by Weight of a water-insoluble methyl acrylate-acrylonitrile resin, the acrylate '-\comprising about 75% thereof which resin is dispersed in unhardened, low jelly strength gelatin of less than 100 grams Shoom jelly strength.

6. The process of preparing a gelatin-free photographic silver image in a water-resistant resin layer on a support comprising the steps of subjecting a photographic element comprising a support and a layer of photosensitive silver halide in a vehicle of 60-95% by weight of a water-insoluble resin selected from the group consisting of the homopolymers of alkyl acrylates, the

alkyl being 1-4 carbon atoms and their copolyrnerswith acrylonitrile in which the level of the acrylonitrile units is no more than about 50% of the total weight of the monomer units dispersed in unhardened, low jelly strength gelatin to the steps of (1) exposing, (2) developing, (3) fixing, and (4) washing in warm Water thereby removing substantially all of the gelatin from the layer.

7. A photographic element from which photographic prints resist-ant to tropical conditions may be prepared which comprises a support bearing a layer comprising photosensitive silver halide and a vehicle therefor composed of about 60-95% by weight of a water-insoluble resin selected from the group consisting of the homopolymers of alkyyl acrylates, the alkyl being l-4 carbon atoms and their copolymers with acrylonitrile in which the level of the acrylonitrile units is no more than about 50% of the total weight or" the monomer units dispersed in unhardened gelatin having a jelly strength of approximately 50 grams Shoom.

References Qited in the file of this patent UNITED STATES PATENTS 2,500,052 Yackel Mar. 7, 1950 2,834,676 Stanley et a1. May 13, 1958 2,848,434 Hallmann Aug. 19, 1958 2,893,867 Dawson et a1. July 7, 1959

Claims

1. A PHOTOGRAPHIC ELEMENT FROM WHICH PHOTOGRAPHIC PRINTS RESISTANT TO TROPICAL CONDITIONS MAY BE PREPARED WHICH COMPRISES A SUPORT BEARING A LAYER COMPRISING PHOTOSENSITIVE SILVER HALIDE AND A VEHICLE THEREFOR COMPOSED OF ABOUT 60-95% BY WEIGHT OF A WATER-INSOLUBLE RESIN SELECTED FROM THE GROUP CONSISTING OF THE HOMOPOLYMERS OF ALKYL ACRYLATES, THE ALKYL BEING 1-4 CARBON ATOMS AND THEIR COPOLYMERS WITH ACRYLONITRILE IN WHICH THE LEVEL OF THE ACRYLONITRILE UNITS IS NO MORE THAN ABOUT 50% OF THE TOTAL WEIGHT OF THE MONOMER UNITS DISPERSED IN UNHARDENED, LOW JELLY STRENGTH GELATIN OF LESS THAN 100 GRAMS SHOOM JELLY STRENGTH.