Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Structurally defined
Reexamination Certificate
2000-01-28
2001-09-18
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Structurally defined
C430S220000, C430S510000, C430S523000, C430S533000, C430S536000, C430S950000
Reexamination Certificate
active
06291148
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the formation of laminated substrate for imaging materials. It particularly relates to improved substrates for photographic materials.
BACKGROUND OF THE INVENTION
In the formation of photographic paper it is known that a white pigmented layer is placed directly under the photosensitive silver halide emulsion. The white pigmented layer is typically a polymer such as polyethylene or polyester in which a white pigment such as TiO
2
is dispersed. Such a layer is highly reflective and opaque and enhances the image sharpness of the exposed and developed image. Furthermore it is known in the art that as the concentration and amount of TiO
2
in the reflective layer under the emulsion is increased that the image sharpness is increased. Sharp images are highly desirable and have significant commercial value.
It has been proposed in U.S. Pat. No. 5,244,861 to utilize biaxially oriented polypropylene sheets laminated to cellulose photographic paper for use as a reflective receiver for the thermal dye transfer imaging process. In the formation of biaxially oriented sheets described in U.S. Pat. No. 5,244,861, a coextruded layer of polypropylene is cast against a water cooled roller and quenched by either immersion in a water bath or by cooling the melt by circulating chill liquid internal to the chill roll. The sheet is then oriented in the machine direction and in the transverse direction. The biaxially orientation process creates a sheet that has a highly pigmented layer on the topside of a voided layer. The pigmented layer provides a highly reflective layer immediately under the image layer. There remains a need to create an image-sharpening layer that provides additional sharpness to a photosensitive silver halide layer without having to additional expensive white pigment such as TiO2. While TiO2 is highly reflective and desirable, it is very expensive and furthermore tends to scatter light in multiple directions, which tends to corrupt the purity of the photosensitive dyes.
In U.S. Pat. No. 5,866,282 it has been proposed to use biaxially oriented polyolefin sheets laminated to photographic grade paper as a photographic support for silver halide imaging systems. In U.S. Pat. No. 5,866,282 numerous advantages are obtained by the use of the high strength biaxially oriented polyolefin sheets. Advantages such as increased opacity, improved image tear resistance and improved image curl. While all of these photographic improvements are possible with the use of biaxially oriented polyolefin sheets, the use of biaxially oriented sheets with solid surface skins for silver halide imaging systems is restricted to the amount of TiO
2
that can be dispersed in the polyolefin polymers as well as to the practical limitation of the thickness of the pigmented and voided layers.
In U.S. Pat. No. 5,888,681 it is disclosed that a photographic element with a microvoided base has some very beneficial attributes in providing an image with an opalescent appearance. This invention is substantially free of TiO
2
to take full advantage of the unique voided layer. While this is highly desirable in certain markets and the images are sharp and pleasing, the overall sharpness is not as high as it could be if TiO
2
was used in a layer under the light sensitive emulsion. Unfortunately when more substantial amounts of TiO
2
are added, the opalescent effect is diminished. There remains a need to provide additional sharpness in an imaging print with minimal use of TiO
2
.
In U.S. Pat. No. 5,429,916 and U.S. Pat. No. 5,466,519 it is disclosed that a multi layers of polymer applied to a base sheet in which the upper layer of polymer is below the silver halide emulsion and also contains more TiO2 than lower layer of polymer. In both these cases the TiO2 is below the silver halide layer and is used for opacity and sharpness. There remains a need to provide addition sharpness to an imaging print without the further addition of expensive white pigment below the photosensitive layer.
PROBLEM TO BE SOLVED
There remains a need for a more effective sharpening agent for photosensitive imaging materials that will provide added sharpness over the conventional means of a pigmented layer under the photosensitive layers.
SUMMARY OF THE INVENTION
An object of the invention is to provide improved imaging materials.
A further object is to provide a base for imaging that has improved sharpness.
A further object is to provide a base for images that will be more durable.
Another object is to provide an imaging material that does not block when stored in stacks.
A further object is to provide a base for imaging that has a reduced propensity for showing scratches.
These and other objects of the invention are accomplished by a photographic element comprising a base material having an upper surface comprising an oriented sheet, at least one photosensitive silver halide layer, and at least one sharpness enhancing agent above said photosensitive silver halide layer.
ADVANTAGEOUS EFFECT OF THE INVENTION
The invention provides an improved imaging element for the casting of photosensitive and image receiving layers. It particularly provides an improved color photographic material that has the required sharpness to provide a pleasing print to the viewer. Being able to provide sharpness by utilization a sharpness-enhancing agent above the emulsion provides a means to increase the sharpness of prints without having to increase the concentration of expensive white pigments such as TiO
2
.
DETAILED DESCRIPTION OF THE INVENTION
There are numerous advantages of the invention over prior practices in the art. The invention provides a photographic as well as an image receiving element that has exceptional sharpness. The exceptional sharp image has significant commercial value as there are many consumers that desire viewing sharp well defined images. Further, the invention provides a photographic element or image receiving base that has less tendency to scratch and show marks and abrasions.
Another advantage of a sharpening agent on the topside of the image is the reduction in the tendency for the imaged prints to stick together. Images in the final customer format are commonly stored as a stack, image side to backside and under a variety of humidity conditions. Being able to provide prints that have a reduced tendency to stick together is a critical enabler for customer satisfaction.
A further advantage of a sharpening agent on the topside of the image is that it creates a softer image that is more appealing in fine arts and portrait markets. Fine art images with a soft subtle appearance is highly desirable for the markets they serve.
An additional advantage was the unexpected and non-obvious discovery that by placing a sharpening agent on the top surface of a photographic image layer that the sharpness was increased without the use of additional expensive pigments such as TiO
2
. Traditionally TiO
2
is used in high concentrations within a layer below the light sensitive silver halide to improve the sharpness of a print. The use of sharpening agent in place of or in conjunction with pigments has a beneficial effect on the final print. There is less unwanted color added to the imaging print with glass beads as opposed to white pigments. This is evident when the sharpness-enhancing agent is used in a layer directly above the image layer.
The terms as used herein, “top”, “upper”, “emulsion side”, and “face” mean the side or towards the side of an imaging member bearing the imaging layers. The terms “bottom”, “lower side”, and “back” mean the side or towards the side of the imaging member opposite from the side bearing the imaging layers or developed image. The term “above” means over or on top of the image or the light sensitive containing silver halide parts of the emulsion. The term “sharpness” refers to the ability to replicate fine details of the image, was measured by mathematical calculations utilizing a method is called the MTF or Modulation Transfer Function. In this test, a fine repeating sinusoidal
Aylward Peter T.
Bourdelais Robert P.
Camp Alphonse D.
McSweeney Gary J.
Eastman Kodak Company
Leipold Paul A.
Schilling Richard L.
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