Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
2000-02-22
2001-11-13
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S527000, C430S528000, C430S529000, C430S530000, C430S967000
Reexamination Certificate
active
06316175
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a radiographic light-sensitive silver halide film material having improved antistatic properties.
BACKGROUND OF THE INVENTION
It is known that hydrophobic resin sheet and web materials of low conductivity readily become electrostatically charged by frictional contact with other elements during their manufacture, e.g. during coating or cutting, and during use, e.g. during the recording of information in exposure devices. Since radiographic film materials, those used for medical diagnostic purposes as well as those used for non-destructive testing methods, have a hydrophobic resin as a support it is no wonder that transport problems tend to occur in the exposure devices as well as in the processors wherein after loading the film into the processor the film runs into a developer station, a fixer station, optionally rinsing stations inbetween and always after said fixer station, followed by drying.
In order to prevent such web materials from being electrostatically charged the “tribo-electrical behaviour” of the said web material has been optimized (e.g. versus polymethylmethacrylate as a reference polymer) in that differences with respect to the said tribo-electrical behaviour between said web material and materials with which contact is made during further handling (especially before, during and after exposure and before processing) are minimized. Useful compounds added to the layers coated onto the resin sheet or web material are e.g. polyoxyethylene compounds, whether or not combined with surfactants having fluoride substituents as has e.g. been described in EP-A's 0 191 491, 0 245 090, 0 260 593, 0 319 951, 0 320 962, 0 370 404, 0 534 006, 0 633 496 and 0 644 454, and in U.S. Pat. Nos. 4,229,524; 4,367,283; 4,388,402; 4,582,781; 4,649,102; 4,916,054; 5,098,821; 5,258,276 and 5,561,032.
Such combination of antistatic agents may provide a so-called “lateral electrical surface resistivity” of about 10
12
&OHgr;/square, measured at a relative humidity of 30%. The said materials are said to provide “non-permanent antistatic properties” due to their “ionic conductivity”. More recently “permanent antistatic properties” have been attained for materials by provision of “electronic conductivity”, thereby reducing the said “lateral electrical resistance” to a value of about 10
6
&OHgr;/square. Such a relatively low resistance has been obtained, particularly in the presence of electronically conducting polymers as e.g. polyethylene dioxythiophene, described in EP-A's 0 253 594,0 292 905, 0 339 340, 0 348 961, 0 440 957, 0 505 955, 0 530 849,0 553 502, 0 554 588, 0 564 911, 0 570 795, 0 593 111, 0 602 713 and 0 628 560, and in U.S. Pat. Nos. 5,279,768; 5,213,714 and 5,306,443.
In most cases the thiophene compounds are comprised in one or more subbing layers of the materials. By reducing the lateral electrical resistance of the light-sensitive silver halide photographic material the positive or negative charges generated after e.g. friction with another material (e.g. inlet in a processing machine) are non-locally distributed over the whole material making decrease the charge density, whereby local concentrations of electrostatic charges are avoided. Moreover it is possible that electrical charges may flow back after interrupting contact with electrically conducting materials. It is clear that such low electrical surface resistivity is highly appreciated.
The said “antistatic layers” may be subbing layers, providing adhesion between the web sheet and the other layers to be coated thereon, wherein said subbing layers are normally coated at both sides of the said web sheet or support. The materials having light-sensitive silver halide emulsion layers at one or both sides of the subbed supports are said to be “single-side” or “double -side” coated respectively.
In case of a single-side coated material the compounds providing antistatic properties may be added to the backing layer(s). Other layers containing antistatic agents and coated onto the subbing layers may be an intermediate gelatinous layer, whether or not containing filter dyes in favour of sharpness, one or more emulsion layers coated adjacent to each other, one or more protective antistress layers and, optionally, an afterlayer. “Handling film materials” should be understood as “loading cassettes” with e.g. radiological films in intensifying screen/film sytems as well as recording films in laser devices for recording digitally stored information on a hard-copy material, which may cause electrostatic phenomena such as “electrostatic sticking” to occur, as well as electrostatic charging or discharging.
Effects of handling caused by electrostatical phenomena can be visually observed on the images obtained after processing of e.g. radiographic film materials which have been run in some processing devices: it has been established that undesired “sparks” are occurring in form of a black line, thereby disturbing the diagnostic value of the image, even when the electrical surface resistance is as low as 10
6
&OHgr;/sq., especially at low relative humidity of about 30%. This is the case with e.g. the trademarked radiographic materials Curix Ortho HTG and Curix Ortho HTL from Agfa-Gevaert N.V., Mortsel, Belgium. It is believed that those spark discharges, are generated by charge transport from electrostatic charges with which an operator is loaded, who brings an unprocessed film material to a processing machine that is connected to the ground: charges are conducted from the operator, through the film after making contact with metal surfaces making part of the said processing machine and further to the ground. The same phenomena may appear in an apparatus wherein metallic parts have been mounted so that they are isolated from the rest of the apparatus and when said metallic parts bear accumulated charges: a discharge may take place through the film, over the operator and further to the earth. As a result “strikes” or “sparks” in form of black lines are found on the film after processing whereby the diagnostic value of the film is highly disturbed.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a light-sensitive silver halide photographic material for diagnostic imaging in medical as well as in non-destructive testing applications, wherein said film has such antistatic properties that spark discharges are avoided, in particular when loading said film material into a processing machine.
It is a further object of the present invention to provide a method of formation of a diagnostic image by means of the said materials.
Further advantages and embodiments of the present invention will become apparent from the following description.
SUMMARY OF THE INVENTION
The objects of the present invention are realized by providing a silver halide photographic material comprising at one or both sides of a subbed support, corresponding with a single-side coated or a double-side coated material respectively, one or more layer(s) comprising a light-sensitive silver halide emulsion, one or more protective antistress layer(s) and, optionally, an outermost afterlayer, wherein at least one of said layers, subbing layer(s) inclusive, further comprises means in order to provide, when conditioned at a relative humidity of at most 30%, an electrical resistance, measured as described in Research Disclosure June 1992, item 33840, of from 4×10
9
&OHgr;/sq. up to 5×10
10
&OHgr;/sq. for the layer having the lowest resistance, more preferably from 1×10
10
&OHgr;/sq. up to 5×10
10 &OHgr;/
sq. and still more preferably up to 2×10
10
&OHgr;/sq., even at a relative humidity of 30% or lower, thanks to the presence of a conductive compound, preferably a polythiophene derivative, and most preferably polyethylene dioxythiophene (PEDT).
This compound is preferably incorporated in the antistatic layer coated upon the subbing layer, making part of the subbing layer unit, wherein said subbing layer unit is in direct contact with the support and wherein said
den Zegel Marc Van
Muys Bavo
Thillo Etienne Van
AGFA-GEVAERT
Breiner & Breiner L.L.C.
Schilling Richard L.
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