Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified backing or protective layer containing
Reexamination Certificate
1999-02-05
2002-11-12
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified backing or protective layer containing
C430S527000, C430S530000, C430S531000, C430S617000, C430S619000, C430S950000
Reexamination Certificate
active
06479227
ABSTRACT:
This invention relates to thermographic recording elements having an antistatic layer or a matte agent-containing layer.
BACKGROUND OF THE INVENTION
From the contemporary standpoints of environmental protection and space saving, it is strongly desired in the photomechanical process field to reduce the quantity of spent solution. Needed in this regard is a technology relating to photothermographic elements for use in reprophotography which can be effectively exposed by means of laser image setters and produce distinct black images having high resolution and sharpness. These photothermographic elements offer to the customer a simple thermographic system which eliminates a need for solution type chemical agents and is not detrimental to the environment.
Photothermographic elements which form photographic images through heat development are disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, D. Morgan and B. Shely, “Thermally Processed Silver Systems” in “Imaging Processes and Materials,” Neblette, 8th Ed., Sturge, V. Walworth and A. Shepp Ed., item 2, 1969.
Thermographic recording elements based on this system are expected to find use in a variety of fields because of their advantages of mono-sheet construction and possible image formation solely by heat treatment.
These chemical-free recording elements (which do not use developers, fixers and other solutions) are more frequently used at relatively low temperature, and thus require a more strict countermeasure for static electricity than conventional photographic silver halide photosensitive materials. If the antistatic countermeasure is insufficient, electrostatic discharge can occur during transportation of recording elements and black pepper-like spots be generated in unexposed areas. Also, since steps from exposure to development are carried out as a single process, the elements are more frequently transported at a high speed. There is a demand for more efficient transportation.
One electrostatic countermeasure known in the art is to provide recording elements with antistatic layers containing conductive polymers, ionic or nonionic surfactants, colloidal silica, metal oxides or compound oxides. Of these, fine particles of metal oxides or compound oxides optionally containing minor amounts of hetero atoms are preferred antistatic agents. Antistatic layers containing such particles are disclosed in JP-B 20736/198, JP-A 20033/1986 and JP-A 39651/1992.
In order to impart sufficient electric conduction to thermographic recording elements, however, these antistatic agents must be added in large amounts at the sacrifice of transparency of the elements. Since the loss of transparency causes to reduce the commercial value of recording elements, there is a demand for an element which is improved in transparency while maintaining conductivity.
As to transportation, it is known in the art to add matte agents to improve transportation. When the above-mentioned antistatic countermeasure is taken, there is a possibility that conductive particles and matte agent fall off due to dynamic contact with the conveyor members during transportation. Especially because the exposure time is reduced by the recent advance of the exposure technology, it is desired to perform the overall process at a higher speed. As the transportation speed and processing speed increase, the fall-off problem becomes serious. An improvement in this regard is desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermographic recording element which is improved in transparency while maintaining conductivity.
Another object of the present invention is to provide a thermographic recording element which is adapted for high-speed processing.
A further object of the present invention is to provide a thermographic recording element having improved transparency, conductivity and high-speed processing adaptability.
In one aspect of the invention, there is provided a thermographic recording element comprising on a support at least one antistatic layer containing conductive metal oxide particles and at least one thermographic recording layer containing an organic silver salt and a reducing agent. The conductive metal oxide particles are acicular particles having a major axis to minor axis ratio of from 3/1 to 50/1.
Preferably, the conductive metal oxide particles are particles of at least one type selected from among ZnO, TiO
2
, SnO
2
, Al
2
O
3
, In
2
O
3
, MgO, and compound oxides thereof, which may further contain a hetero atom. More preferably, the conductive metal oxide particles are particles of SnO
2
doped with antimony.
One preferred embodiment is a one-side thermographic recording element having the thermographic recording layer only on one surface of the support. The thermographic recording element further has at least two back layers on the opposite surface of the support. The outermost layer of the back layers contains a hydrophobic polymer binder and at least one layer of the back layers other than the outermost layer contains a matte agent.
In another aspect of the invention, there is provided a thermographic recording element comprising a support having a pair of opposed surfaces, at least one thermographic recording layer containing an organic silver salt and a reducing agent on one surface of the support, and at least two layers on the other surface of the support. The outermost layer of the at least two layers contains a hydrophobic polymer binder and at least one layer of the at least two layers other than the outermost layer contains a matte agent.
Preferably, the outermost layer is based on a binder containing at least 75% by weight of a water-dispersible polymer latex, and has a thickness of 0.2 to 10 &mgr;m.
DETAILED DESCRIPTION OF THE INVENTION
The thermographic recording element of the invention has a thermographic recording layer containing an organic silver salt and a reducing agent. One preferred embodiment of the invention is a one-side thermographic recording element having a thermographic recording layer only on one surface of a support. In the thermographic recording element of the preferred embodiment, an antistatic layer is provided on the back surface of the support opposite to the thermographic recording layer. The antistatic layer contains acicular conductive metal oxide particles having an aspect ratio of from 3 to 50. The use of such acicular conductive metal oxide particles as the antistatic agent is effective for suppressing the generation of black spots by static electricity and thus improving transparency and increasing the commodity value. In contrast, spherical conductive metal oxide particles are difficult to meet both the requirements of suppression of black spot generation and transparency, and when added in a large amount sufficient to suppress black spot generation, will detract from transparency. The aspect ratio is limited to the range of from 3 to 50 because the acicular shape effect is lost with an aspect ratio of less than 3 and particles with an aspect ratio of more than 50 are impractical.
In another preferred embodiment of the invention, a one-side thermographic recording element has at least two back layers on the back surface of the support. The outermost layer of the back layers contains a hydrophobic polymer as the binder and at least one layer of the back layers other than the outermost layer contains a matte agent. This construction is effective for improving mar resistance and preventing particles from peeling off even during high-speed transportation. These effects become outstanding particularly with the embodiment having the above-described antistatic layer. To prevent antistatic agent particles from falling off, it is preferred that the layer of the back layers other than the outermost layer, for example, the matte agent-containing layer be an antistatic layer. If the matte agent is added to the outermost layer, matte agent particles will fall off during transportation and the element becomes practically unacceptable. If a hydrophilic polymer such as gelatin rather t
Kubo Toshiaki
Nakayama Naohiro
Chea Thorl
Fuji Photo Film Co. , Ltd.
LandOfFree
Thermographic recording elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermographic recording elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermographic recording elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2987108