Radiation imagery chemistry: process – composition – or product th – Post imaging processing – With structural limitation
Reexamination Certificate
2001-04-27
2002-08-13
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Post imaging processing
With structural limitation
C430S531000, C430S935000
Reexamination Certificate
active
06432623
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of processing a photographic imaging element to obtain a protective overcoat that provides resistance to fingerprints, common stains, and spills. The overcoat formulation comprises at least one water-dispersible hydrophobic polymer interspersed with a water-soluble polymer. The imaged photographic element is dried at an elevated temperature to facilitate coalescence of the hydrophobic polymer in the overcoat, thereby providing enhanced stain resistance and water resistance.
BACKGROUND OF THE INVENTION
Silver halide photographic elements contain light sensitive silver halide in a hydrophilic emulsion. An image is formed in the element by exposing the silver halide to light, or to other actinic radiation, and developing the exposed silver halide to reduce it to elemental silver.
In color photographic elements, a dye image is formed as a consequence of silver halide development by one of several different processes. The most common is to allow a by-product of silver halide development, oxidized silver halide developing agent, to react with a dye forming compound called a coupler. The silver and unreacted silver halide are then removed from the photographic element, leaving a dye image.
In either case, formation of the image commonly involves liquid processing with aqueous solutions that must penetrate the surface of the element to come into contact with silver halide and coupler. Thus, gelatin or similar natural or synthetic hydrophilic polymers have proven to be the binders of choice for silver halide photographic elements. Unfortunately, when gelatin or similar polymers are formulated so as to facilitate contact between the silver halide crystals and aqueous processing solutions, the resultant coatings are not as fingerprint and stain resistant as would be desirable, particularly in view of the handling or environment that an imaged photographic element may commonly experience at various times and circumstances. Thus, fingerprints can permanently mark the imaged element. The imaged element can be easily stained by common household products, such as foods or beverages, for example, coffee spills.
There have been attempts over the years to provide protective layers for gelatin based photographic systems that will protect the images from damages by water or aqueous solutions. U.S. Pat. No. 2,173,480 describes a method of applying a colloidal suspension to moist film as the last step of photographic processing before drying. A series of patents describes methods of solvent coating a protective layer on the image after photographic processing is completed and are described in U.S. Pat. Nos. 2,259,009, 2,331,746, 2,798,004, 3,113,867, 3,190,197, 3,415,670 and 3,733,293. U.S. Pat. No. 5,376,434 describes a protective layer formed on a photographic print by coating and drying a latex on a gelatin-containing layer bearing an image. Various lamination techniques are known and practiced in the trade. U.S. Pat. Nos. 3,397,980, 3,697,277 and 4,999,266 describe methods of laminating a polymeric sheet film, as a protective layer, on a processed image.
Protective coatings that need to be applied to the image after it is formed, several of which were mentioned above, adds a significant cost to the final imaged product. Thus, the processing equipment needs to be modified and the personnel running the processing operation need to be trained to apply the protective coating. A number of patents have been directed to water-resistant protective coatings that can be applied to a photographic element prior to development. For example, U.S. Pat. No. 2,706,686 describes the formation of a lacquer finish for photographic emulsions, with the aim of providing water- and fingerprint-resistance by coating the light-sensitive layer, prior to exposure, with a porous layer that has a high degree of water permeability to the processing solutions. After processing, the lacquer layer is fused and coalesced into a continuous, impervious coating. More recently, U.S. Pat. No. 5,853,926 to Bohan et al. discloses a protective coating for a photographic element, involving the application of an aqueous coating comprising polymer particles and a soft polymer latex binder. This coating allows for appropriate diffusion of photographic processing solutions, and does not require a coating operation after exposure and processing. Again, however, the hydrophobic polymer particles must be fused to form a protective coating that is continuous and water-impermeable.
U.S. Pat. No. 5,856,051 describes the use of hydrophobic particles with gelatin as the binder in an overcoat formulation. This invention demonstrated an aqueous coatable, water-resistant protective overcoat that can be incorporated into the photographic product, allows for appropriate diffusion of photographic processing solutions, and does not require a coating operation after exposure and processing. The hydrophobic polymers exemplified in U.S. Pat. No. 5,856,051 include polyethylene have a melting temperature (Tm) of 55 to 200° C., and are therefore capable of forming a water-resistant layer by fusing the layer at a temperature higher than the Tm of the polymer after the sample has been processed to generate the image. The coating solution is aqueous and can be incorporated in the manufacturing coating operation without any equipment modification. Again, however, fusing is required by the photofinishing laboratories to render the protective overcoat water-resistant. Similarly, commonly assigned U.S. Ser. No. 09/353,939 and U.S. Ser. No. 09/548,514, respectively, describe the use of a polystyrene-based material and a polyurethane-based material, with gelatin as the binder, in an overcoat for a photographic element, which overcoat can be fused into a water resistant overcoat after photographic processing is accomplished to generate an image.
Commonly assigned U.S. Ser. No. 09/235,436 discloses the use of a processing solution permeable overcoat that is composed of a urethane-vinyl copolymer having acid functionalities. Commonly assigned U.S. Ser. No. 09/235,437 and U.S. Pat. No. 6,194,130 B1 disclose the use of a second polymer such as a gelatin or polyvinyl alcohol to improve processibility and reduce coating defects. Commonly assigned U.S. Ser. No. 09/621,267 discloses the use of a processing solution permeable overcoat that is composed of various non-gelatin containing water-dispersible polymers in combination with a water-soluble polymer.
While the prior art has disclosed imaging elements with a processing permeable overcoat that is rendered water impermeable, and the materials used to prepare such overcoats, it has not been specific in how these imaging elements have been prepared. The desired overcoat may be applied in several possible methods. It may be applied to a imaging element that is previously coated with all layers except the overcoat. In such a case, the overcoat may be applied as a single layer. It also could be applied in a single coating operation, in a tandem method. In this case all the layers, except the desired overcoat can be applied at a first station in the coating machine. The web is then dried and run through a second coating station, without winding it up, where the overcoat is applied.
The most preferred method for coating an overcoat is at a single coating station, along with the other imaging layers. This is typically accomplished with gelatin overcoats using a slide hopper where multiple solutions are layered without mixing. The layered solutions are then deposited on the web either by bead coating or by dropping it as a curtain onto the web.
PROBLEM TO BE SOLVED BY THE INVENTION
A polymeric latex protective overcoat when coated simultaneously with underlying emulsion layers in a so-called single pass operation, during manufacture of a photographic imaging element, has been found not to deliver the same stain protection features observed when coated separately in a so-called “two-pass” coating operation. Thus, it has been found that the functionality of the overcoats empl
Donovan Kevin M.
Lobo Lloyd A.
Konkol Chris P.
Le Hoa Van
LandOfFree
Method for processing a photographic element comprising a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for processing a photographic element comprising a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for processing a photographic element comprising a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2918647