Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified backing or protective layer containing
Reexamination Certificate
1999-09-09
2001-03-27
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified backing or protective layer containing
C430S536000, C430S538000, C428S535000, C428S537500, C162S130000, C162S145000, C162S146000, C162S157600
Reexamination Certificate
active
06207362
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to imaging materials. In a preferred form it relates to base materials for photographic papers.
BACKGROUND OF THE INVENTION
In the formation of photographic paper it is known that the base paper has applied thereto a layer of polyolefin resin, typically polyethylene. This layer serves to provide waterproofing to the paper and provide a smooth surface on which the photosensitive layers are formed. The formation of the smooth surface is controlled by both the roughness of the chill roll where the polyolefin resin is cast, the amount of resin applied to the base paper surface and the roughness of the base paper. Since the addition of polyolefin resin does not significantly improve the tear resistance or tear strength of the base paper, the tear resistance of typical photographic paper is a function of the tear resistance of the cellulose paper base. Typical photographic paper bases have a tear resistance between 70 and 140 N.
Typical photographic grade cellulose paper base has a particularly objectionable roughness in the spatial frequency range of 0.30 to 6.35 mm. In this spatial frequency range, a surface roughness average greater than 0.50 micrometers can be objectionable to consumers. Visual roughness greater than 0.50 micrometers in usually referred to as orange peel. An imaging element with roughness less than 1.10 &mgr;m at a spatial frequency of between 200 cycles/mm and 1300 cycles/mm is considered smooth and is typically defined as a glossy image.
It has been proposed in U.S. Pat. No. 5,866,282 Bourdelais et al. to utilize a composite support material with laminated biaxially oriented polyolefin sheets as a photographic imaging material. In U.S. Pat. No. 5,866,282, biaxially oriented polyolefin sheets are extrusion laminated to cellulose paper to create a support for silver halide imaging layers. The biaxially oriented sheets described in U.S. Pat. No. 5,866,282 have a microvoided layer in combination with coextruded layers that contain white pigments. The composite imaging support structure described in U.S. Pat. No. 5,866,282 has been found to be more durable, and more tear resistant sharper and provide brighter reflective images than prior art photographic paper imaging supports that use cast melt extruded polyethylene layers coated on cellulose paper. The tear resistance of the paper base in U.S. Pat. No. 5,866,282 is between 100 and 160 N.
It has been proposed in U.S. Pat. No. 5,244,861 to utilize biaxially oriented polypropylene laminated to a base paper for use as a reflective imaging receiver for thermal dye transfer imaging. While the invention does provide an excellent material for the thermal dye transfer imaging process, this invention can not be used for imaging systems that are gelatin based such as silver halide and ink jet because of the sensitivity of the gel imaging systems to humidity. The humidity sensitivity of the gel imaging layer creates unwanted imaging element curl. One factor contributing to the imaging element curl is the ratio of base paper stiffness in the machine direction to the cross direction. Traditional photographic base papers have a machine direction to cross direction stiffness ratio, as measured by Young's modulus ratio, of approximately 2.0. For a composite photographic material with biaxially oriented polyolefin sheets laminated to a base paper it would be desirable if the machine direction to cross direction stiffness ratio for the paper were approximately 1.6 to reduce imaging element curl.
A receiving element with cellulose paper support for use in thermal dye transfer has been proposed in U.S. Pat. No. 5,288,690 (Warner et al.). While the cellulose paper in U.S. Pat. No. 5,288,690 solved many of the problems existing with thermal dye transfer printing on a laminated cellulose paper, this cellulose paper is not suitable for a laminated cellulose photographic paper since this paper has undesirable surface roughness in the spatial frequency range of 0.30 to 6.35 mm and the pulp used in U.S. Pat. No. 5,288,690 is expensive compared to alternative pulps. Further, the paper base discussed in U.S. Pat. No. 5,288,690 has a tear strength of between 80 and 150 N.
PROBLEM TO BE SOLVED BY THE INVENTION
There remains a need for a more effective base paper to provide an improved smooth surface as well as provide a tear resistant photographic element.
SUMMARY OF THE INVENTION
An object of the invention is to provide an imaging material that has improved strength properties.
A further object of this invention is to provide a base paper that provides a tear resistant photographic element.
Another object of this invention is to improve the durability of the imaging material.
These and other objects of the invention are accomplished by an imaging element comprising a base comprising a cellulose fiber containing paper, wherein said paper has a tear resistance of between 200 and 1800 Newton.
ADVANTAGEOUS EFFECT OF THE INVENTION
The invention provides an improved paper for imaging elements. It particularly provides an improved paper for imaging elements that are smoother, more tear resistant and are low cost compared to a substrate made from polymer.
DETAILED DESCRIPTION OF THE INVENTION
There are numerous advantages of the invention over prior practices in the art. The invention provides tear resistance to a. reflective image that will improve the durability of images as they are viewed, handled and stored by consumers. Tear resistant images are perceptually preferred and thus have significant commercial value, over images that tear easily and thus are subjected to damage during viewing, handling and storage. Tear resistance also improves the efficiency of the imaging materials to be transported though digital printing equipment such as ink jet printers as well as the silver halide printing and development equipment. A tear resistant imaging material tends to reduce the frequency of web breaks in equipment thereby improving printing productivity. Tear resistance also is desirable for applications such as display materials that require a tear resistant support materials. Currently display materials are post process laminated to improve tear resistance, a tear resistant paper would reduce the need for expensive post process lamination for tear resistance. Further, the invention provides an imaging element that is strong and has has a smoother surface, increasing the commercial value of the imaging element by providing a glossy reflective print material. Another advantage is the significant reduction in cellulose paper dust generation as this base paper is cut in both the cross and machine directions in imaging converting applications such as the slitting of wide rolls of imaging support, punching of imaging elements as in photographic processing equipment and chopping in photographic finishing equipment. Replacing the cellulose fibers with non cellulose paper fibers reduces dusting. These and other advantages will be apparent from the detailed description below.
In order to provide an imaging element with sufficient tear resistance, the tear resistance of the base cellulose paper has been increased over prior art cellulose base papers. It has been found that a base comprising a cellulose fiber containing paper, wherein said paper has a tear resistance of between 200 and 1800 Newton provides an imaging element with tear resistance. A tear strength less than 180 N is not perceptually different from prior art materials. A tear strength greater than 2000 N exceeds the ability of a typical consumer to tear an image. Since it is difficult to obtain tear resistance above 200 N with cellulose fiber alone, the paper of this invention requires additional materials for a tear strength above 200 N. By adding high strength materials to the paper prior to forming on a wire or applying a coating to the paper after formation on the wire, the tear strength of the paper is improved as the high strength materials contribute to the tear resistance of the base paper. It has been found that the addition of polymer fib
Aylward Peter T.
Bourdelais Robert P.
Dagan Sandra J.
Eastman Kodak Company
Leipold Paul A.
Schilling Richard L.
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