Coating processes – Measuring – testing – or indicating
Reexamination Certificate
2001-11-15
2003-10-28
Bareford, Katherine A. (Department: 1762)
Coating processes
Measuring, testing, or indicating
C427S458000, C427S470000, C427S471000, C427S402000, C427S420000
Reexamination Certificate
active
06638565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coating method and apparatus, and more specifically to a method and apparatus for eliminating static charge from a support when a coating solution for forming an emulsion layer of a heat development-type photosensitive material is to be applied onto the support.
2. Description of the Related Art
In recent years, in the fields of films for medical diagnosis and photographic films for plate-making, it has been strongly desired, from the standpoints of environmental protection and space-saving, to reduce the volume of processing waste fluids. Thus, there is a need for technologies relating to thermally developable photosensitive materials (heat development-type photosensitive materials), as films for medical diagnosis or photographic films for plate-making which can be efficiently exposed by a laser image setter or a laser imager to form clear black images having high resolution and sharpness. These heat development-type photosensitive materials are advantageous in providing customers with a thermal processing system that does not need liquid-type processing solutions, and which is simple and not harmful to the environment.
Photosensitive materials can be roughly divided into two types: silver halide photographic photosensitive materials in which gelatin-based binders are used and heat development-type photosensitive materials, in which polymer latex-based binders such as SBR (styrene/butadiene copolymer) are used. For both types of photosensitive material, a coating solution for a silver halide photographic photosensitive material or a coating solution for a heat development-type photosensitive material is applied onto a support web which is being continuously moved.
However, unlike silver halide photographic photosensitive materials, in the case of producing a heat development-type photosensitive material, there is a tendency, depending on subbing layers, for levels of electrostatic charge on the support to increase. Consequently, foreign matter such as dust particles tends to be easily attracted and adhered onto the support by static before the coating solution is applied. Further, because, unlike the gelatins used as binders for silver halide photographic photosensitive materials, the polymer latexes used as binders in heat development-type photosensitive materials cannot set (gelate), when the aforementioned foreign matter adheres thereto, layer surface defects in the coating layer tend to become noticeable even if the foreign particles are small. Thus, heat development-type photosensitive materials have a drawback in that the surface of the coated layer is susceptible to foreign matter causing layer surface defects when at least a coating solution for forming an emulsion layer is applied onto the support.
As well as heat development-type photosensitive materials frequently exhibiting such layer surface defects due to large amounts of static electricity on supports as described above, silver halide photographic photosensitive materials also suffer such layer surface defects if amounts of static charge on supports during production are high.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-described circumstances. It is an object of the present invention to provide a coating method and apparatus to greatly reduce layer surface defects, which are caused by adhesion of foreign matter such as dust particles and the like to a coated layer formed by application of a coating solution onto a support.
In order to achieve the above object, the method according to the present invention is characterized in that, while at least a coating solution for an emulsion layer is being applied onto a continuously moving support web, static charge of the support is reduced to a level of at most 1 kV shortly before the coating solution for the emulsion layer is applied to the support web.
Also in order to achieve the above object, the apparatus according to the present invention is characterized in that, while at least a coating solution for an emulsion layer is being applied to a continuously moving support web, a static reducing device, which reduces the level of static charge on the support before application of the coating solution for the emulsion layer, is provided.
In accordance with the present invention, layer surface defects resulting from adhesion of foreign matter, such as dust, can be prevented from occurring, because the static charge level of a continuously moving support is made to be not more than 1 kV just before a coating solution is applied for forming at least an emulsion layer.
REFERENCES:
patent: 4835004 (1989-05-01), Kawanishi
patent: 5424174 (1995-06-01), Motokazu et al.
patent: 6027871 (2000-02-01), Katoh
Bareford Katherine A.
Fuji Photo Film Co. , Ltd.
Young & Thompson
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