Photography – Fluid-treating apparatus – Heating – cooling – or temperature detecting
Reexamination Certificate
2003-12-19
2004-11-02
Rutledge, D. (Department: 2851)
Photography
Fluid-treating apparatus
Heating, cooling, or temperature detecting
C219S216000
Reexamination Certificate
active
06811333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal development apparatus for heating and developing photothermographic imaging material.
2. Description of Related Art
In a thermal development process for heating and developing a photothermographic imaging film (hereinafter, simply named “film”), as disclosed in Japanese Translation of PCT Patent Application (Tokuhyohei) No. H10-500497, a member obtained by coating a surface layer of a heating drum with an elastic member (silicon rubber) having heat resistance and high thermal conductivity has been put to practical use as a heating means for heating the film.
Particularly, in a thermal development unit for developing a silver salt photothermographic imaging film obtained by using the organic solvent, when the film is developed, a surface active agent of a surface layer of the film and/or the organic solvent or an organic acid of an emulsion layer are liberated from the film and attach to an elastic member (silicon rubber) forming the surface layer of the heating drum. Therefore, the elastic member (silicon rubber) deteriorates, and the swelling and abrasion of the elastic member (silicon rubber) is generated. Accordingly, a problem is arisen that the finished image having a stable quality cannot be obtained.
To solve the problem, in the Published Japanese Patent Application (Tokugan) No. 2002-208438, there is a technique of coating the surface layer made of the elastic member (silicon rubber) having the high thermal conductivity with fluororesin such as Teflon (trade name) to prevent the elastic member (silicon rubber) of the high thermal conductivity from being attacked by the surface active agent included in the surface layer of the film and/or the organic solvent or the organic acid of the emulsion layer in the developing of the film. This technique prevents the elastic member such as silicon rubber from gradually deteriorating with the elapsing of time. Accordingly, the finished image of the stable quality can be obtained.
However, when the surface of the elastic layer is coated with the fluororesin, though the lengthened life time of the heating drum and the lengthened cycle of the cleaning and maintenance of the heating drum can be achieved, there are following problems peculiar to the fluororesin.
(1) The carrying force caused by the low friction factor is insufficient.
(2) The development is made inactive because of the lowering of the thermal conductivity.
(3) The film is not tightly in contact with the drum in an axial direction of the drum, and a certain volume of air layer is generated between the film and the drum.
The problem (1) will be described hereinafter. As is well-known, Teflon (trade name) is the material having a low friction factor and is used as a sliding member. Therefore, when the nipping pressure of the opposed rollers arranged around the heating drum is set in the same condition as that in case of the heating drum with the elastic member of silicon rubber, the film carrying force during the thermal development drastically lowered, and there is a probability that the film slips on the drum. The slipping of the film causes the lengthening of the entire development period of time practically. This may cause a change in the density of the image, wrinkles or damage on the surface of the film.
The advance of the development of the photothermographic imaging film is determined by the product of the heating temperature and the heating time. Therefore, when the constant heating time, in other words, the constant film carrying speed is not maintained during the carrying from the top to the end of the film, the unevenness in the density of the image occurs. Therefore, in the thermal development apparatus having the heating drum with the surface layer made of the elastic member such as silicon rubber corresponding to the earlier art, to prevent the unevenness in the density of the image and the unevenness of wrinkles, the carrying speed in the thermal development unit and the carrying speeds on the upstream and downstream sides of the thermal development unit are set to the relation of (carrying speed on upstream side)<(carrying speed in thermal development unit)<(carrying speed on downstream side).
The problems (2) and (3) will be described hereinafter. The effective supplying of heat energy to the photothermographic imaging film, the obtaining of the finished image of the desired density and the suppression of the photographic fog on the film in the thermal development apparatus are achieved by thermally developing and carrying the film while pressing the film on the surface of the elastic member (silicon rubber) of the high thermal conductivity by the opposed rollers. However, because the thermal conductivity of Teflon (trade mark) is approximately one-third of that of the elastic member used in the earlier art, the inactiveness of the development occurs in the film when layer of Teflon is excessively thick, and the finished image having the desired density cannot be obtained.
Further, when the film is nipped between the opposed roller and the heating drum having the silicon rubber layer on its surface, even though the parallel relation between the heating drum and the opposed roller is not obtained in the axial direction of the heating drum in some degree of precision, the elastic layer of silicon rubber makes the film be able to uniformly and be tightly in contact with the heating drum and the opposed roller. On the other hand, in case of the existence of the surface layer coated with Teflon (trade mark), when the nipping pressure of the opposed roller and the parallelism are set in the same condition as those in the case of the heating drum with the silicon rubber, there is a probability that the film is not uniformly and tightly in contact with the heating drum and the opposed roller. Therefore, while considering the problem (1), it is important to optimize the biasing force of the opposed rollers and the alignment between the heating drum and each opposed roller, with more emphasis of the tight contact of the film with the heated surface than that in the earlier art.
Because the air layer is generated between the drum and the film due to the non-tight contact of the film with the drum in the axial direction of the drum, the heat transfer from the drum to the film further deteriorates in case of the coating of the drum with fluororesin, and the density in the final image is undesirably lowered. In case of the use of the drum coated with fluororesin, it was found out by the experiment of the inventors that there is/are a steep change(s) in the distribution of temperatures in the neighborhood of the surface of the drum, as compared with the case of the use of the drum coated with silicon rubber. Therefore, when the contact of the film with the drum is not sufficient, the heating of (or the heat transfer to) the film is changed, and the unevenness in the density of the image is enlarged as compared with that in the earlier art. Accordingly, the tight contact of the film F with the heated surface must be emphasized as compared with in the earlier art, and it is important to optimize the biasing force of the opposed rollers and the alignment between the heating drum and each opposed roller.
Further, when the number of opposed rollers is small in the opposed roller method, it is difficult that the film is tightly in contact with the drum at a curvature of the drum surface in the carrying direction. Particularly, a small volume of vacancy is formed between the drum and the opposed roller each time the film faces the opposed roller, and the unevenness in the density of the image can be easily formed.
In case of the use of the drum coated with fluororesin, it was found out by the experiment of the inventors that there is/are a steep change(s) in the distribution of temperatures in the neighborhood of the surface of the drum, as compared with the case of the use of the drum coated with silicon rubber. Therefore, when the contact of the film with the drum is not
Kido Kazuhiro
Sumi Makoto
Umeki Mamoru
Cantor & Colburn LLP
Konica Minolta Holdings Inc.
Rutledge D.
LandOfFree
Thermal development apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal development apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal development apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3289250